Is this because they know some whales that want the +1 model are going to jump at the opportunity to buy whatever is on the market, and then buy again when higher-range models are released?
Buyers who walk into an Apple store for a base MacBook Pro will wait if they hear a new model is coming out. So if you have a buyer basing purchases on the generation number, it makes sense to launch that model as soon as possible.
Pro/Max buyers generally are checking into specs and getting what they need. Hence the M2 Ultra still being for sale, for some niches that have specific requirements.