Huh, turns out Doom 2 has code for horizontally sliding doors for the Wolf3d secret levels, but they commented it out.

there's av ideo of someone testing it out after reenabling it and... hm. https://www.youtube.com/watch?v=DF3hQfo9ju0

... I think ... that's why they commented it out. For two secret levels it seems like a waste to code that in, and it looks... messy.