Or, more logically and realistically, the amount of windows users that update tethered is not worth prioritising, as the vast majority do it OTA.
Windows iTunes will get an update, but obviously there’s not enough users for them to prioritise that over iOS, tvOS, audioOS and other Apple related updates before them. Can’t blame them for looking after customers using their own platform first, and rolling out to the handful of windows users that tethered update their devices.
You just have to wait for it, cos you’re a lower priority than over 95% of the user base. The amount of people that tether update is drastically small these days, compared to the user base of iPhones. People go for the route of less hassle.