It definitely serves as a differentiation between Pro and base, and I'm sure they'll get some additional pro upgrades by people just looking at a piece of paper

It definitely serves as a differentiation between Pro and base, and I'm sure they'll get some additional pro upgrades by people just looking at a piece of paper and deciding that they must have USB 3. However the lack of USB 3 IO on the existing chip from last year is a very real limitation. The Raspberry Pi 4 supports USB 3 via a separate host controller (the VL805) communicated with over PCI-e, given that the core SoC doesn't have the IO blocks...basically the same deal. That VL805 by itself is almost the size of the A16. Now of course Apple could make a USB 3 host controller dramatically smaller, but then they'd have a new SoC.