/vr/ - Retro Games

Why does one sky texture work out of the box, but the other doesn't?
I know having split sky textures like this might cause issues, but this is purely for demonstrative purposes, and it happens with the texture on the right all the time anyway, yet the texture on the left, all I have to do is set the ceiling texture to it and boom it works.
Please, I'm making the most revolutionary WAD ever, I just need to solve this and I will make history.