there are a few different points. first of all not all mantis styles are the same. they are different from hong kong to the north of the mainland and taiwan.
so the original statement can not be made for all mantis styles. some put more power and jing into their movement than others along with more waist movement.
second force equals weight X speed so your force generated can be increased by the speed of your strikes.
then the physics behind your strikes, unfortunately, there are many that don't even know how to punch correctly or generate power correctly over even do a stance correctly so a lot comes into play.
a bullet won't kill you if i throw it at you, it will kill you if i shoot it at you. the speed increases generating more force.
not just in mantis but it should be in all martial arts, there is a reason for each type of strike, how and why it is used and it's speed or power. if not, then you only need to learn one strike as they would all be the same.