It's not about the stimulus. It's about the fact that some exercises are naturally better done within the lower rep range (5-10), while others work and feel better with the higher rep range (20-30). Some are better in the middle.
With DB side raises, take too high of a weight, and you will feel like you can't do anything productive done (can't even raise to an appropriate height). With lower weights you can get a proper range of motion and can really feel the burn and get the target (sic!) muscle exhausted.
Additionally, too high of a weight doesn't feel good on joints.
Similarly with squats (or deadlifts). Squating with 5-10RM is fine. But 30RM?.. Theoretically it gives the same stimulus as doing 5-10RM, but practically everyone who suggests putting such sets to a program should be medicated and put on a suicide watch. The taxationvon all systems of your body is just so huge (especially the more advanced you are).
Heck, mere squating true (!) 20RM (just one set!) is considered a crazy challenge that most will never do. I have done crazy stuff in my life, but I am not embarrassed to admit that this challenge is beyond me. Simply doing 20RM leg extensions is hard enough for me.
These require the practical experience. Take barbell/dumbbells, try yourself and no more explanations will be needed.
My point is that there is nothing a priori about it, its just a question of what your goal is, what you are adapted to do and how the resistance curve of the movement is set up.
If you have a cardiovascular system that can grind through 20RM squat sets and you like it, go off. It'll be hard for most people due to the large amount of muscle mass recruited, but on the other hand, if you can load a lateral raise 5RM with acceptable range of motion, why the hell not. It just doesn't work well with dumbbells in particular.
Most people don't build up to such a stimulus, so its not surprising if its uncomfortable, if all youve ever done is 20 rep sets.