I'm no expert, but I can't possibly see how this could be the case. I have never seen any weird trophy offers below master 1, boost or no boost. From what I know, the amount of bases rises exponentially as you go down each tier (at least until low crystal), so the number of people who would have to be playing at once to drop this phenomenon from master 1 to crystal 2 or lower is astronomical.
The "casual players playing for longer periods" explanation has another flaw: if an update/1-gem boost/lots of free time would make casual players play more, why wouldn't it affect inactives similarly? With all this new stuff, surely people who play occasionally in general would stop on to make a few raids each day, actually putting them in the queue more often than normal.
Finally, here's my last and possibly best reason. As you've seen in low Champ, the bases available follow a similar pattern. First, you get a few "normal" offers (13+ trophies), then you get some 12s, then 11s, then 10s, then 9s, and so on down the line. Sure, you get the odd higher offer thrown in if that defender has just gone offline, but the pattern is pretty straightforward. If this was indeed not a bug, the same sort of thing would be happening in crystal: the people who are seeing 1s and 2s would have seen 6s, 5s, and 4s before the lowest offers. But they haven't, indicating that matchmaking is simply not working as its supposed to.



