I once had an explanation for the timing in this scene worked out which, sadly, I no longer remember.

It's the drugs, man... ;-)

I've always thought it was poignant and realistic for Curt and Brian to have such a major meltdown over something that's not obvious.

Yes, I agree, like a lot of the legends, rumors and gossip that make up the story, it's perfect that there is no definitive reason why they argued and broke up.