- Pre-Purchases. If you offer your product for pre-purchase outside of Steam, and that pre-purchase grants the user a Steam product key, those keys should unlock your product at the same time it is made available for purchase via Steam. You should also not give Steam customers a worse deal than Steam Key purchasers.
I don't see any breaks of this rule --> So it should be ok to grant keys for pre-purchasers outside Steam (on itch.io). You just need to contact Steam Support and clarify that question. Until that - all above mentioned is considered as lies. IMO