I thought they were supposed to do the whole “last version of Windows that will be updated forever” with Windows 10, and of course abandoned that some time ago.

My gut feeling is that their product management marketing folks came to the conclusion that Windows as a subscription was not going to work for the consumer market where the OS is something that’s just part of the device you buy. And in discussions with system OEMs they made the decision that consumers like it when the version number goes up, so increasing that windows number every several years will move systems.