So from what I have gathered, and from another post I made linking specifically what Keits said on stream (I’ll find it and edit in the link for you), what you’re saying is wrong.
You can buy the game by signing in with the profile you intend to use/are using on Windows 10 on PC or Xbox One, then it is part of your purchases and on your account wherever you go (you’ll have to download it again if you want to play it on a platform that doesn’t already have the game but you don’t pay for it again). For new PC users, they can just buy the game, install it on their Windows 10 and start playing. If, however, you have been playing the game on the console previously and want your saves and progress to cross over, you will have to start S3 once on the console to get it synced up.