Anti-competitive practice to benefit itself? Yes, Apple sure has done this, as has Epic and every business ever. A monopoly though? I mean I guess, as much as Epic has a monopoly on its App Store.
Apple is controlling access to customers with iOS devices. There is no alternative.
Epic is not. Any competitor can sell to the same people that buy from Epic's store.
And they're warring about the commission on ... in app purchases ... on a predatory free game aimed at teenagers?