app stores are not equal
On android you can go to other non "play" app stores or sideload whatever you like (after making some trivial security settings changes).
AFAIK (not an apple phone user as not got money to burn, & also occasionally do android coding so having a physical android phone more useful than iPhone, even though its more snoopy / less secure) on apple devices sideloading is not really a viable option and the apple app store is the only option. (Please correct me if I'm wrong on this).
So with apple its essentially blocking Fortnite full stop.
With android its blocking Fortnite from the obvious app find and install store but users can go to a different app store or sideload.