I'm wagering that's the 2021 model getting extra prototyping. 5G is change worth extra antenna testing. I would assume micro-led's warrant extra testing too.We've known for quite some time now that there will be two refreshes this year. Ming-Chi Kuo is a pretty reliable source.
As for why they'd do that, idk.
However, it could be like the iPhone X in that it represents a big jump, will have a matching big price, and the features will trickle down the line over the next year or so.