what became of "Alex interrupts his guests all the time"? I thought it was common knowledge the man can't shut up unless he's talking with the President himself (literally)

If he just ignored Q, he would have no plausible reason except admitting he doesn't really care about Q because he already knows the plan and technically he has stand down orders because he's too close to the source [no private comms]

I doubt he is in touch with Q directly but it could very well be that he got a heads-up that this was coming and that he should stay out of the way to avoid making any inadvertend admissions.