Apple is acting as a leader in reducing the footprint of general computing hardware; albeit their devices have among the longest service lives, they continue to be further restricted in their operation over time. There is a danger here with the population switching en masse from using PCs to using Phones as their primary computing devices. Forcing it to allow third party marketplaces might be a start in reversing that trend.
Epic is a leader in the development of anxiety-driven consumer software. Fortnite's primary capital isn't the player's competitive standing, it's the uniqueness of their cosmetic gear. They target the most vulnerable and maleable markets, tweens and children, and ply them with social anxiety; one of the most insidious and emotionally distressing devices for that age group. See also, yesterday's lengthy discussion. [0]
So I kind of hope that the EU allows third party stores, but allows Apple to place curation constraints on the sort of purchases that are available to users.