Most bullies, especially clique-based ones, never consider themselves bullies. Their herd mentality allows them to justify their actions bc they see their besties are doing the same thing, and bc all the shit talking behind the victim's back has already painted the victim as the "bad guy" and deserving of the clique's dislike and maybe even malicious actions. So I'm not surprised if the members genuinely don't think they've done anything wrong.
What I'm personally focusing on is whether Hyunjoo truly felt mocked, outcast or tormented by them. Bc if she did, then that's really all that matters. She was bullied then, regardless of whether the members did it intentionally or not, whether they thought their actions were justified or not.
And I'm inclined to believe she did feel tormented, to the point her mental health suffered, because:
1. Her brother was able to produce the medical records of her suicide attempt dated only a day after the "kimbap incident"
2. Countless videos have surfaced of the members mocking and laughing at Hyunjoo (especially for her way of speaking), with Hyunjoo not laughing with them, but rather complaining about their mockery and looking upset. If the person you're mocking isn't in on the joke, then that's just bullying imo.
Also I find it really telling that the members show zero sympathy for Hyunjoo's health, despite the public suicide record. They've all spoken about this issue a number of times now, and every time their focus is entirely on themselves, they've never extended any concern, sympathy or well-wishes for Hyunjoo. Which Hyunjoo has for them.