Fair point.
I do think Steam is engaged in anti-competitive behavior, but that doesn't mean they're the full equivalent of the app store. And we can see on the PC market the large number of indie games that very literally would not exist if PCs were locked into only using Steam.
My point here is more that Steam is not really a good argument for justifying a pricing model. But it's a good clarification that in many ways Steam has "only" mostly locked down the PC gaming market, where Apple has gone further and locked down the actual software that can be loaded onto the phone.