This is completely incorrect. Their contract states that you can’t sell Steam keys for less elsewhere, which is entirely fair in my opinion. If your game is on multiple platforms or storefronts, you can sell it for whatever price you want there. The fact is that nobody does; they list it for the same everywhere and pocket the difference if someone buys on EGS.
The suggestion here is that the type of game that can thrive on a subscription service is either a small one that benefits from better curation and visibility or a live-service one that can make up revenue on the backend by charging all the new players microtransactions (the new store shelves are inside the games themselves).
I’ve been saying this since Game Pass launched: it encourages scummy monetization. The kind of games that come to it are going to have more and more content locked away behind microtransactions to make up the money lost by not selling copies. It’s going to gradually become full of “free” to play garbage, and people will accept it because they didn’t pay for an individual game outright.