Or games could be in multiple stores.

You could go to a game store... and it would have... all of the games.

Like a real-ass brick-and-mortar store, and physical glass-disc games in little plastic boxes.

Valve has not been an obstacle to that possibility, but Steam's 30% cut says they don't mind de facto exclusivity. They're not charging you like they're abusing their monopoly... but they're charging game developers the same as bastards like Nintendo and Apple.

The article is entirely about how that monopoly holds back the industry. There is one store. You're on it, or you're fucked. And getting there requires sacrificing an entire third of revenue, straight off the top. For obvious reasons developers and publishers would rather not do that. Valve has them by the balls - and a gentle grip doesn't really defuse that situation.