This was done on purpose, so fully aware of it. I used to not do this years ago, but noticed most, if not all, CSGO maps did have the bottom clip missing. For a long time I wondered why that was and I guess it's because sometimes the bottom clip extends beyond a corner and also acts as some sort of notice to the player when he's getting up on a stair while strafing or moving backwards.
I adopted it and it has become my default way to clip a stair. I'll have to check how newer (official and custom) maps do it nowadays and might revisit it
Thanks for the feedback and the album!