you dont need heavier loads if you do them properly
Yes, but I just think all exercises work better using heavier weights - as long as execution is close to perfect

What do many bodybuilders attribute their good traps to? Deadlifts. And there's almost zero range of motion. But of course there are bodybuilders who claim, for example, that you don't need heavy dumbell curls if done "properly," 20lbs is all you'll ever need. Usually if I did something "heavy" I usually did a perfect slow, squeezing and contracting set too

Deadlifts can build tremendous traps and there is no range of motion to speak of, just contracting and stretching of the traps. The most important variable is the androgens, because there are no "bodybuilding traps" without exogenous androgens.

Some lifters claim they saw zero additional growth with "proper bodybuilding sets."

Dante Doggcrapp claimed just hard stretching in itself builds som muscle and I know he's right.

I often did a single set of shrugs and then finished with just holding the dumbells in a stretch for as long as I could tolerate it, could be 30 seconds or could be 3 minutes, hurts like a son of a bitch. Sitting in a stretch, then contracting as hard as possible against the weight for 20 seconds or whatever, then stretching again.
