It is true to a degree as everyone outlined above. If you exert too much strength you WILL rip your muscles or tendons off etc.. and in nature, that is a showstopper ie if you rip a muscle in the wild, you might end up dead. Tendons and ligaments even worse. Or at least very dysfunctional.
Often people using steroids develop increases in muscle strength far faster than their tendons can grow / strengthen to match the muscle strength and this can cause injury.
Also this phenomenon was part of the theory behind the comic "Incredible Hulk" - because in times of severe emergency the body just lets go and you can draw on super phenomenal strength e.g a woman lifting a car off her child. The whole Hulk thing was a very interesting premise.
Furthermore people who go insane often recruit far more of their strength and they are just plain scary and very difficult to pin down.
I believe many of the old world strongmen through years of training developed very strong tendons and ligaments and therefore were strong despite not being overly huge. Similarly, people who have done hard labour for a long time.
There were some strongmen of old who had "double tendons" - a genetic anomoly as whacky as people who have extra fingers but far more useful. Imagine being born with tendons and ligaments thicker and stronger than normal. The advantages would be incredible.
I believe that static holds of extreme heavy weights are good for stimulating tendons and ligaments strength ... monkeys also come to mind, hanging statically off branches etc.. they have very strong connective tissue. And not mega-bulky muscle.