[ExpertAdvisor01]

"You should use Steam Keys to sell your game on other stores in a similar way to how you sell your game on Steam. It is important that you don’t give Steam customers a worse deal than Steam Key purchasers."

https://partner.steamgames.com/doc/features/keys

[scraptor]

This only applies to steam keys sold off site, which is why the original comment specified non-steam keys.