^^ Your seriously gonna take a "Youtube" description as actual proof it will release fully (not lobotomized) on the PC? I gotta bridge in London I'd like to sell you...
Ok, if you don't want to believe the description of the video, of the official YouTube channel of Halo, then take a look at this news article written by Chris Lee, the Studio Head of 343 Industries. He doesn't specifically mention Infinite being on windows, but he includes the official game engine demo announcement trailer for Halo Infinite on the official Xbox YouTube channel. On that video, the description, again, is literally the same, word by word. The only difference is that the first video I provided has 5 million views, where as the Official Xbox trailer has 1 million. They're both official. Lol.
Edit: I would also like to show you a list of all games that are Xbox One and Windows 10 Exclusive.
Halo Wars 2
Forza Horizon 4
We Happy Few
Sea of Thieves
State of Decay 2
Also, here is an Xbox Wire recap article on E3 2018. It lists Halo Infinite as an Xbox One and Windows 10 Exclusive. If you don't believe Xbox, then I don't know what to tell you.