> I wonder what about the design makes it a rocket compared to what I would assume is a pretty standard design?

Injuries nonwithstanding, the quality of the seal means it was an exceptionally well designed item for the purpose of storing 99% water.

side note: there's a reason you get a visit from the FBI if you buy ten pressure cookers (e.g. if you find a great Black Friday deal and have a large family and plan Christmas gifts...)