Maybe some of them talk about this but as far as I know, I have never seen any idols from the 3rd gen talk negatively about their juniors' manners. Some of them even dislike it since it caused them too much struggle back then too. You know how they trying to lessen it even their fans not that nice but the idols themselves really open about this. I forgot who say this but he said it's unnecessary for junior to greet them at the waiting room as they know it's tiring to record the music show performance. Many of them actually talking about how they didn't really like that kind of formality.
Maybe some of you don't know but the seniority culture in Korea is as bad as their bullying issues. I have many Korean friends from my work place talking about the difference in seniority culture between my country and theirs. They can get a warning letter if they didn't bow to their senior even when they didn't notice them.