I'm talking about towards the end of the Blue Bird, Red Queen chapters (12 I believe)

I get where you're coming from, especially because Natsume doesn't fully buy into it either. He definitely benefitted from using Natsume in the broader situation so there's obvious truth in what you say, but the friends line I'm referring to, I do not believe was tied to him trying to get something out of Natsume in that moment. It's more so Ibara having a very transactional and warped understanding of what friendship is. It's not fake, it's just not normal. I don't think Ibara wanting to befriend Natsume was a tactic at all especially because he asks to talk /after/ everything is over.

Afterwards, Ibara does also say "on a matter unrelated to Eden" that he would like to apologise, and then also talks about how he's conniving at The Same Time. That being said, with Ibara knowing that Natsume is aware of when he's lying, I guess my question would be that if Ibara knows he sounds insincere, why extend his apologies and ask to be his friend anyways if he didn't mean it? It would kind of just be an unnecessary hassle.

Basically A lot of it is Ibara being defensive of his image. Wonder Game was the catalyst for Ibara deciding that maybe he should tone it down a little and stop being god awful, and I do think that the reason this comes off as insincere at face value is because it was the first time he'd actually (onscreen) attempted to be apologetic. A lot of it I think is him trying to defend his own ego because he's a little embarrassed post Nagisa calling him out for his behaviour Combined with him actually taking those criticisms to heart.