I think Assembly eliminated 64k years ago, because 4k for all practical purposes had become the new 64k, and 64k entries had been scarce and not super impressive for a while.
At Revision 2015 to 2017, the PC 64k compo was absolutely insane, with production values exceeding pretty much every other category, including unconstrained PC demos. If 4k is the new 64k, 64k at that time became the new PC demo.
256 bytes is the big (hum...) thing now. With one ridiculous entry that managed to pack 8 different effects, with music and transitions https://www.pouet.net/prod.php?which=85227
The 4k category was blown wide open in 2009 by rgba/tbc with Elevated [1] (live reactions: [2]). It demonstrated that 4k was more than sufficient for impressive effects and music -- suddenly, 64k was no longer an interesting constraint.
https://www.youtube.com/watch?v=tirAdWbceak
To be honest, it looks like a techno video from the 90s to me.