Well removing those makes it not solid anymore. If you change a part of the level that was intended it can become broken again.
You're right
Hence that's why I was hesitant to restore some of the numerous changes I made to my R3 from the previous contest in fear that some of the same broken stuff in solutions will pop up again. I honestly don't know why I didn't heed this advice that I've been subconsciously aware of since the previous LDC.
Because of that, R1 made the stacker a pickup again which shouldn't had been taken away in the first place, and in R2 added some more terrain at the top and restored the exit limits for the two exits to be able to only take two lemmings each (again, as you said I shouldn't had taken it away since it did play a part in forcing the intended solution, and they've been there since the very first version!
). Because the exit limits cannot be seen, I put in green circus lights in the shape of the number 2 next to those exits to make this not hidden information!