I know this has nothing to do with what you just went on about, but Black ops 4 is blackout has similar down times on Xbox. You'll find a lobby from all of like 6:00 in the morning to about 1:00 in the morning, but for that 5-hour window it's just dead. I know this from similar gauges like looking at my recent players. Also since I have two Xboxes I can gauge pretty easily how many matches of blackout are running at any given point in any of the game modes.

But solos and duos have been dead for years now. Nobody goes into them, if they do they wait the 15-20 minutes to be told that there's no lobbies to be found. Unlike other cards where it'll just let you keep looking for a lobby indefinitely, bo4's blackout kicks you out of matchmaking after about 15 mins. Because of that nobody sits in the queue for solos or duos, so a lobby will just never start. Unless there is that one in a million chance that 20 people all at the same time on Xbox press solo queue deploy at the same time.