In 1.21.2 Mojang fixed the sneak slime glitch, which is the most used glitch used in speedruns, because of that, from now on, all the old runs are moved into 1.20~1.21.1 category, and the default category is now 1.21.2+.

You can still submit Pre-1.21.2 runs if you want, just don't forget to choose it.