Just won the Tangled Depths meta as pug map; minutes later we get the "volunteer" popup to go to a new map

Title says it all--my TD map was not low population and we'd just completed the meta event successfully, after a lot of work. Still, we got the "move to a new map, because we're closing this one" notification.

I would love to know whether ArenaNet is aware of, let alone working on, this bug. Or anyway, I'd like to assume it's a bug--maybe it's a feature? And in that case, what's its intention?

I haven't seen it mentioned in the forum dev tracker recently. And Colin's recent replies, while very much appreciated, don't appear to have included anything about this.

Edit: for those of you who think "oh so people left after meta ended?" I mean people were still getting the chest when we got the popup. No one leaves after winning the TD meta without getting the chest. That's silly. I didn't screen cap it, but I looked at the chat as everyone started expressing disbelief in map chat. My timestamps showed 2 minutes between the end of the event and people being pissed off about the map population notification.

Anyone who's experienced this in Dragon's Stand knows what I'm talking about, since people actually do that meta event.

Edit 2: if I had to guess, I'd say that they have a weighted measurement that includes a "population flux" term, and that this term is weighted too heavily.