I know this post is a little late, but I figured people might want to hear my thoughts on this.
I chose to vote for “allow everywhere except on the last turn”, so here's why.
In the MKW community, we have a very clear definition for what constitutes an “ultra shortcut”, since every glitch in the game is only possible because of a single mistake in the way checkpoints are programmed. This applies to MG, MC, CM, WGM, GV, RR, rPB, GV2, rSL, SGB, rWS, and DKJP, which makes rigidly defining an ultra shortcut category extremely easy and uncontroversial. However, this definition doesn’t apply to every shortcut we casually refer to as “glitches”, since BCWii, BC3, rDH, and DKM all have unintentional shortcuts that we consider to be separate to the no glitch category, even though they don’t involve the checkpoint bug. Now, why is this exactly? The short answer is...

You might think there’s a clear answer for why we consider these shortcuts to be glitch categories, but there really isn’t. For example, one might say that we consider BCWii’s glitch to be illegal for no glitch because you pass through a wall that doesn’t have any collision, but that’s nothing more than an explanation we use to justify a decision people in the community made long before most of us were even involved with the game. Logically, there’s no reason why we’d consider the BC3 shortcut as a separate category while shortcuts like the DKSC double cut are unquestionably no glitch, but the community has never had an issue with many of the game’s large shortcuts, and that’s mostly because they were discovered so early on that they were already an established part of the no glitch runs by the time people began to start defining glitches, and not because there’s anything uniquely glitchy about the BC3 shortcut over the DKSC double cut.
In the case of the DS Desert Hills shortcut, it’s a bit easier to defend its status as a “glitch”, since we’ve sort of unofficially decided that certain wall clips aren’t allowed for no glitch. However, this isn’t to say that
all wall clips constitute a glitch, either. To give an example, if we viewed all wall clips as illegal regardless of context, then Blake’s 1:46.262 run would have spawned a new glitch category on DKSC (
https://youtu.be/7X_J9xSaPpY?t=23). As a matter of fact, this could mean that every track in the game could have its own glitch by virtue of people setting runs that use a wall clip. The truth is, we only consider wall clips to be illegal when they can be used to save time.
Now, you might be asking what any of this has to do with MG wall ride, but I think this highlights an important truth about how we designate categories in this game.
Mr. Bean has recently shown us that the mechanic that allows for the wall ride shortcut is simply a consequence of the speed lock created by the mushrooms, and seemed to conclude from it that the wall ride gap shortcut should be considered legal for no glitch.
However, as I’ve just laid out, it’s never really about the mechanic itself that creates a shortcut category, since none of the “shortcut” categories in this entire game follow any sort of internal consistency, as they’re really nothing more than the result of archaic rules conceived long before we knew anything about the game.
Just like how the community decided early on that the BCWii glitch isn’t allowed for no glitch, we similarly decided that the MG wall ride shortcut shouldn’t be allowed either. Just like every other non-checkpoint bug shortcut, this would likely be an uncontroversial decision today if it weren’t for a few problems we’ve since run into. Since BCWii, DKM, BC3, and rDH all lack a true ultra shortcut category, we simply just put their respective shortcuts in the place of where the ultra would go. Since the community chose to not stress any real differences between glitches that exploited the checkpoint bug and those that didn’t, this created the mindset that there could only ever be a single type of glitch category per track, which is where we ended up running into some issues on tracks that happened to have both. This includes Grumble Volcano, DK’s Jungle Parkway, and - pertinent to the discussion - Mushroom Gorge.
My belief is that if the designation for MG wall ride is retroactively allowed into the no glitch category, then it would only make sense to deem practically every other shortcut category, such as rDH or BCWii, legal for no glitch. It’s an undeniable fact that any “shortcut” category that doesn’t involve the checkpoint lap detection glitch has some degree of subjectivity to it, and I don’t think there’s anything wrong with making these categories separate to no glitch.
The community decided to make BCWii and BC3 shortcuts separate categories because players wanted to preserve the integrity of the preexisting categories, which is completely fine, and shouldn’t be considered shortsighted or illogical. We today simply choose to acknowledge these as “glitches” because of how old they are, and because of the importance placed on times that don’t use them, even with the modern knowledge that they don’t fit the definition of a glitch at all. Most speedrunning communities have no problem acknowledging the existence of multiple categories (think SM64’s 0, 1, 16, 70, and 120 star categories), so I’ve never understood the stigma around going beyond this two category per track rule. Nintendo only gave us one official leaderboard per track, so the dichotomy between glitch and no glitch has always been artificial to begin with, so why not expand it to fit our modern understanding of the game?
As a matter of fact, I feel like this discussion should instead revolve around how we even define these shortcut categories in the first place. If you ask me, I say we have two separate categories for glitch and no glitch runs, then if there happens to be a different, significant shortcut that people play and regard with high importance, we should give it its own separate, equal WR and leaderboard. Most speedrunning communities I’m familiar with seem to continue recognizing old, historically important routes as their own categories even if a faster one is discovered, allowing for more variety than just any% or 100%, and I feel like the MKW community could learn something from this.