Anecdotally, I've reached the same conclusion. United wants to grab as many suckers as it can before releasing saver awards.
In my view, it's a four part devaluation of miles that has become particularly acute over the last year or so.
1.) Remove historical practice of swinging the doors open on saver availability very close in / day of
2.) Remove capacity far out
3.) Reduce saver award availability generally
4.) Increase time required to locate awards, thereby increasing search costs and decreasing efforts to redeem
1 and 2 hit Plats+ particularly hard (since they can book far out with no change penalties, and book close in with no close-in fees). It is a big middle finger from MP.