I wouldnt call that enough. Its somewhat true to an extent... Not in this case...
Its basically only for smaller snakes in adult size aquariums. I would use 30 or 40 gallon. my snakes tank is 36"x12.5" wide and shes only 1 year old. I started her in the same tank from a baby.
It really depends on how secure they feel in the tank. If its wide open and empty theyre going to get stressed out..