There is one aspect that no one has mentioned.
When you play games on Steam, you log in with your Steam account. This is how you access your games, there are no other log in credentials required. I've never had to use any other credentials for any of the games I own and play in over 10 years.
You create 'player or user names' in games obviously, but that game is linked to your Steam account, the player name doesn't matter, it's just linked to your account.
If I open WGT in Steam, is it going to take me to the game log in screen? It can't. That won't work with Steam awards and such, those are tied into your Steam account. There's no association on WGT with my Steam credentials so there's no way to link the login with my Steam account.
You won't be able to launch the game outside of Steam, it won't work. If I go into the 'steam apps' folder for Steam on my computer and try and run a game .exe I will get an error telling me that 'Steam needs to be running'... WGT/TG can't have two versions of the game available for play, the Steam version will be the only one you can use and it has to be launched from within Steam.
So how is WGT going to keep a linked association between the existing accounts at WGT and Steam accounts?
I'm sure they've thought about this issue, Steam has ways to link games through other platforms, Twitch, Discord etc.... I've just never seen WGT post anything about this anywhere, if they have and addressed it, just ignore this and delete the post.
If not, can anyone at WGT comment on the subject?