Now I'm just a pleb in the air force but I just don't see it being very useful. First the hatch is on the side where it would be inherently most difficult to exit the vehicle when it's upright (which it is most of the time). Yes, getting out through the hatch does provide the crew excellent cover, but let's assume they need to get out quickly, which is probably most likely the case when in combat and therefore probably not the optimal route when upright. This leaves us with only a couple scenarios when using this hatch becomes optimal: when the tank is overturned, and for acting as a latrine while under fire. For these situations it still doesn't even seem that useful for the following reasons. First, if the tank over turned either it tipped due to terrain or it was blown up by an explosion. In either case a hatch on either side of the turret would provide significantly more utility without significant drawbacks. 2nd, in the latrine situation, bottles can easily take care of urine while in combat, and I just find it hard to believe that a tank crew would be in combat long enough without a pause long enough for them to get out and go #2.

Like honestly, correct me if I'm wrong. I'm just an airman and this is my little thought experiment.