Yes consoles prevent side loading too, and it's exactly as wrong there too, though, I would also say there is an argument that a phone is in a different class of necessity than a game console, and could easily be argued to require different rules and consumer/society protections. A phone not only is a central and practically required part of general life today, companies like Apple and Google go further and perform many many actions to insinuate and embed and integrate and entangle their phone and their attached ecosystem into as many aspects of the users life as possible. They are not neutral, and the resulting user entrapment is not of their users own choice and creation, even though there are no guns to any heads. Apple and Google are absolutely equivalent to Phillip Morris when it comes to the users voluntarily consuming a product that is bad for them.
Point of all that is, phones are not game consoles, and not only would that be true naturally just because of how one is a necessary tool for conducting life, while the other is not, the valid culpability of the phone maker is even more compounded when you factor their own actions to amplify the users dependence on them. They actively seek it and do many different things to get it and strengthen it, from advertising to policy to tech functionality. You can't do that, and still be innocent of responsibility for it's effects.
The only valid thing I see is the argument that if Epic agree to the same deal from MS and Sony, meaning all the same significant factors not just the cost, then it will require some non-trivial argument to claim that Apple has harmed them.