As you might imagine, I do have a theory. But a few screens first, from the Store in the last 24 hours:
We'd been used to the large banners at the top of the Store home being for PC or XBox titles, that's understandable advertising space for the best of Windows 10. But to have non-Mobile-relevant titles listed on the phone seems out of line. In many cases, even with a 'not available' (or similar) message, there's also a 'Get' button lit up. Tapping it quickly makes the button vanish, since there is, in fact, nothing to install, of course.
One theory is that this is all getting ready for the mass market availability of 'Windows 10 on ARM', i.e. the Store client is being simplified and is more relaxed as to which titles it actually displays, relying on the app to be identified as incompatible on non-relevant devices, rather than having everything filtered at the server end. Continuing this thought, maybe it's just to reduce server load? The 'working' 'Get' control is certainly just a bug.
I'll let Microsoft off if it does in fact mean that a) the Store is generally faster, and b) this is one of the preparatory steps to the release of more Windows 10 ARM-based tablets, hybrids and, yes, folding devices.
Comments? Is there a better theory?