Those things aren't necessarily mutually exclusive anymore. Something like a Dell 7270 will cost about £275 on eBay. 12 inch screen and 1080p touchscreen. Some question the wisdom of a small screen like that with scaling and whatnot but I've always found it fine.

That's fair. Though I wonder how many people buy computers on ebay as opposed to dell.com or amazon.com or an actual brick-and-mortar store.

That said, I suspect most people over the age of 35 or so can't read text at "normal" size on a 1080p 12inch screen, so if they want a 12 inch screen they have to either scale up their text or drop the resolution. And I believe the reported resolution in the Firefox telemetry is the one the OS thinks it's using, not the one the hardware has.