Agreeing to a TOS is a standard for open markets. Splitting hairs over a TOS existing is ignoring the fact that Epic doesn't allow third parties to sell in their market (with or without a TOS).

When you accept Apple's developer agreement, you're agreeing to a contract. It absolutely isn't an "open market" for any definition of what that means. Apple has exclusive control of their IP and they are offering a way for you to license it on their terms.

Regardless of what term you use it's a fact of reality that right now no one else but Epic can put content on the Epic Store which is not true of Apple and the App Store.