From the timeline, and from remembering past launches, I'm pretty sure it was well past Max-Q.

I think Max-Q occured about a minute before. You can review the stream, it passed supersonic way before (you see the shock cone on the two sides), then max-q, then a minute later the explosion

same feeling here. anyway, you could see the cap going off before rocket was self destructed. dunno if was part of the sequence.

the engine exhaust plume expansion reminded of that time they lost a nozzle due to high pressure, but again hard to tell if it was cause or effect from the armchair

Indeed it was around main engine cutoff.

This launch, the feed from SpaceX had all of those events marked in a timeline - a new feature. From the large number of people speculating about the timing of these events, it would seem that you were all watching some other livestream? Perhaps the NASA one?

Might want to check out the SpaceX stream next time.

Edit: the SpaceX website doesn't appear to have a recording of their live stream available.