Bloomberg cites two high-profile cases referenced in the ongoing lawsuit, one involving Ubisoft, and another Warner Bros.
First of all, I trust Ubi and WB way less than valve.
Valve allegedly threatened to delist all editions of Rainbow Six Siege after Ubisoft offered a cheaper option on its Uplay store.
Yeah.
Because it violates their policy. That's not a "threat", those are the terms of the contract Ubi and WB agreed to. Terms that everyone has to follow.
Heck, Ubi and WB should be hit with a counter suit for trying to leverage their market position to exert control over valve and getting unusually favorable terms.
Clown suit. Ubi and WB are mad they can't break their contract with valve in a one sided way.
edit: I forgot some context:
The deal between valve and a publisher or dev is: they can sell on steam and elsewhere if steam is at least tied in price, or cheaper, but when they sell somewhere else, that includes the steam key and access to steam and steam's distribution at no cost.
What the devs and publishers wanted to do was leverage other features of steam and the steam ecosystem, while undercutting steam's price.
They are always free to just not sell on steam for a cheaper price. That's not what this is about.
edit2:
https://partner.steamgames.com/doc/features/keys
"Steam Key Rules and Guidelines"