I hate non-upgradability as much as the next HN user, but it's worth noting that external USB SSDs (Samsung T7 and others) are now pushing 1GB/second at lower and lower prices. I recently got a 2TB model for $220 or so.

I say that not to excuse Apple, but perhaps some others are like me and are surprised at how fast the portable models have gotten.

That's possible and perhaps likely, alas.

So yeah, if we're in the universe where there's zero expandability, and their silicon is super powerful with low heat requirements, I guess they may as well make it smaller.