Apple already has mechanisms in place to allow side loading so there is no new work they need f to add. People that jail-broke iOS and side load apps also prove that technically is possible.
When companies do anti-competitive things they are forced by the society with laws to stop, without this kind of laws we would still have mobile phones that are locked forever to a network, still have a big tax when you call someone on a different network, still have a big tax when you would transfer to a different back or use other bank ATM(this examples are from EU not sure about other regions).
For example the laws related to preventing fires also FORCE companies to add more exit doors, use the correct materials, add fire suppression equipment etc. A few years back some night club bribed the fire department and opened without respecting this laws, around 100 young people died because some greedy bastards didn't want to do the correct thing.
Anyway, my comment was about the argument "I love Apple to protect me" that argument is NULL.
We can attempt to debate the actual market share of Apple, to define the actual markets, to decide if Apple and Google are actually competing or have an hidden agreement, to define how we measure the damage by the market abuse (if any), to determine fixes for this abuses (if any).