All of these issues are because nobody ever tested the map before it was placed in mAAp. Actually, Ice has been in mAAp for a long time but Assist only recently garnered a community so this is technically the first time people are being exposed to the map. The reason you can go under the ice is because of an engine limitation. For whatever reason, the game decided that certain flat surfaces have no collision. I didn't know that until I saw people play Ice. You can also fall out of the map in many places because I never finished the map lol.
I actually beta tested Ice for v6.0 and there were a lot of spots you could crawl out of the map on.

But back then you couldn't go under the ice and you actually slid when walking on it if I remember correctly.