I see most of the runs are done in js0.23 (the web version, a.k.a classic.minecraft.net), however there is actually an issue with this - Mojang have updated this multiple times over 2019 and possibly even 2020, changing random things, and I believe this may include the physics, which would affect speedruns. I can confirm that it atleast has been updated over time as I have downloaded multiple archived versions of js0.23 from Omniarchive, and they all have peculiar differences (for example, later versions appear to have a glitched Steve model).

On top of this, I also see that the original 0.0.23a_01 is allowed. However, this version has completely different physics and gravity to the Javascript remake. Shouldn't there be some guidelines on what version of the game to use?

I would suggest making the original version of 0.0.23a_01 the only allowed version of the game to use, as the web version is actually slightly renowned in the classic Minecraft community for being buggy and a bit of a poor effort on Mojang's behalf, not to mention the inconsistencies between updates. However, I also understand that trying to install such version in question, and installing a launcher to actually run it properly (like MultiMC) might be a bit of a pain for newcomers, making the Javascript remake much more accessible to play.

Any thoughts on this?

Super Game made games intended to be played on Dendy region consoles. Although it is hard to tell with this game as it does not use the original game's music, opting for original tracks instead, their other ports which do use the original music, are at a wrong, faster tempo, but the right pitch on NTSC. On PAL, they are at the right tempo, but wrong pitch. On Dendy, the tempo and pitch is just right.

In other words, just because a game plays on NTSC or PAL doesn't mean it's playing properly.

This game is intended to be run in Dendy mode.

There are different revisions of this game that have major changes, including the addition of title cards for some levels, and even adding a new level altogether (Lorenzen's Soil). WR could therefore be invalid.

Even real time can be inconsistent. The timings of physics, transitions, stuff like how long an enemy is "stunned" before it dies, etc, can be inconsistent depending on the version of Scratch.

It does appear that all runs are being run on Scratch 3, however, as I said, since Scratch 3 does not have 100% backwards compatibility, there are some bugs that shouldn't happen, and incorrect timing. A download of Scratch 2 can be found here https://scratch.mit.edu/download/scratch2 , the official online version is no longer available however the download version may lag on some PCs, so if this is the case. you can use https://s2online.github.io , which is just a re-hosted version of Scratch 2 with extra features.

FYI: the timings of this game heavily depend on what version of scratch you're running it in. there does not seem to be any rule about this. the game was made for scratch 2 and it should be run in that, yet the WR is running in scratch 3, which is not 100% compatible with programs made for previous versions, so there may be some bugs that don't appear in previous versions of scratch, and as i said, large timing differences (sometimes even into the seconds).