I don't feel pull/chin ups are at all the same. Even now I'm decent at them and do weighted for heavy low rep, I just don't feel it the same way. I have no science, just never that thing where you finish a set and think '**** that was hard'.
When it comes to squats, I don't think it is so much the weight as it being so more muscle/movement involved. I think first you have to be able to grind reps to feel it, that's a skill in itself. But beyond that, I don't think the weight so much matters (absolute or relative to BW), just that it's effort for you. I can't back squat so just do front so weight is less and it feels just as hard even though my heavy sets are usually just 85-95kg.