Giants throw boulders starting at 19 strength.In many/most editions (at least 3e, 4e, & 5e) strength is related to level. In 5e most classes can't get past 20 strength until after lvl 20. Strength over 20 is specifically "epic" and past level 20 in 5e.
So again, what level gives you the strength to do that? Why do keep ducking the question?
Or are you suggesting if I had a level 5 character with 50 strength when every other lvl 5 character has 18 strength that is somehow balanced? Or is balance and illusion and not important?
To be honest, balance is not that important to me.
a human can throw a boulder of their relative size with the same 19 strength.
So a commoner born with 19 strength can throw a boulder