Except for their strong arm tactics forcing software companies to not be able to sell their games cheaper on other platforms:
AFAIK, this restriction doesn’t apply if you’re distributing via a different market place.
If that’s true, that seems fair since you’re relying on Valve’s infrastructure to support the sale.
Humble Bundle 100% does both, sells games cheaper and redeemable through Steam keys, and has been doing so for many years.