Simon and GGP combined do own an overwhelming percentage of all retail square footage in the US, but lets at least consider the rest of the argument here.

Apple's "shelf space" is not free. There are constant R&D expenses involved in introducing new sensors and screens that make the underlying apps better. They take on the support load of on-boarding users, managing the relationship, and dealing with any problems. Advertising, carrier validation, third party hardware ecosystem, etc.

Epic wants to sidestep all of the costs of building a platform, and offload support costs onto Apple.

> Simon and GGP combined do own an overwhelming percentage of all retail square footage in the US

This is factually incorrect, and not only incorrect, but so wildly far from being correct that one wonders if this statement was made in bad faith. They only have around 300 million sqft out of an estimated 12 billion sqft, around 2.5%. That is not an overwhelming percentage, nor is it "99.9999% of all retail square footage in the world", which was not a hyperbolic statement. Competitors in retail can obtain their own shelf space. You cannot obtain your own shelf space for mobile software. The network effects of hardware+OS centralization are too strong, so there are and never will be any viable competitors to iOS and Android.

> Apple's "shelf space" is not free. There are constant R&D expenses involved in introducing new sensors and screens that make the underlying apps better.

The R&D expenses do not change regardless of whether there are 1 million or 10 million apps available for iOS. Allowing people to distribute their own software comes at no cost to Apple.

> They take on the support load of on-boarding users, managing the relationship, and dealing with any problems.

Apple absolutely does not do any of this as it pertains to individual apps.

> Epic wants to sidestep all of the costs of building a platform, and offload support costs onto Apple

Nobody is asking for Apple's support; really, what the world needs is less of Apple's involvement in the hardware the people own, not more. Epic is clearly willing to spend money on building platforms, since it has a documented $600 million in losses in its effort to build a competitor to Steam. This, however, is not a case where it is possible to build a platform.