https://www.gamespot.com/articles/microsoft-not-ready-to-confirm-if-halo-infinite-su/1100-6460675/

It was recently discovered that Halo Infinite may not support Microsoft's nice Xbox Play Anywhere system whereby you can play its Xbox and PC versions with a single purchase. The game's page on Xbox.com didn't list Xbox Play Anywhere as a supported feature, leading some to believe the sci-fi shooter wouldn't be included in the program.

Microsoft has now issued a statement on the matter, though it doesn't clear anything up and may raise more questions.