I built this today.  It was an interesting design.  The body is heavy and I was surprised the legs held it.  Turns out, the legs lack hinged joints; problem solved.  The interior has a bed of sorts but really is a place to dump all the unused accessories or figures when storing assembled.

It was a quick build, less than an hour. i like it.  I assume Lego only had limited still shots to work with which is why we don't have the alien beast or some sort of representation if it inside the tank.  Also why we probably did not get Baby Yoda's hover crib.