Do I have to link my Steam account to my Xbox Live account even tho never played on Xbox?

I played on my computer but not on Steam but they made me sign up for an Xbox Live account. Now I want to play thru Steam since I had to uninstall the game anyways. Does the game consider my Xbox Live account a different platform?

Yes, it will consider both Xbox and windows 10 ver as different platforms. Also, you need to re-install the game to get access to the link code to use it on the steam ver. so you can get access to your account. Unless you can get access to your chars on Xbox. You won't be able to link the accounts if you went started the game.

Your XBOX Live Account is your Microsoft Account. As long as the XBOX account is linked to an MS account, they are both considered one account and they share your gamertag between xbox and Microsoft itself. The gamer tag is all that is really important. XBOX and Windows 10 versions are linked as one by default, though, so they natively share progress between XBOX and Windows 10