But, at the end of the day, Walmart can't prevent customers from proceeding to Kroger down the street to get the products or deals they want. That's the market regulator of last resort in most circumstances.

You say "Apple doesn't have a monopoly on phones or games". In the broad view, you may be right, but they've spent significant effort in creating a closed ecosystem with non-trivial switching costs, inside of which they DO have complete gatekeeping power. They may not have a full "prevent the customers from going to Kroger" power, but they can basically say "here's a several hundred dollar toll to leave our store, and BTW, we won't let you back in for anything else we sell", which is a pretty high barrier. Is the only available counterweight for their behaviour "drop everything and buy a new $500 phone to express your discontent?"

Google gets out of this with their hands much cleaner-- they can retreat to "Well, you can sideload apps". Epic proved they can make that a viable business that way on Android. But iOS offers nothing resembling that without asking consumers to jailbreak their devices, which is probably beyond reasonable accommodation.

I'm sort of amazed they're so desperate to cling to the no-sideload mentality. Offering sideloading with a lot of big angry red warnings immediately defuses the vast majority of anti-competition complaints, while still being scary enough that most name-brand software isn't going to immediately drop off the App Store. I'd also think it presents a welcoming option for some hobby developers, where even the $100 annual developer fees are prohibitive, until they can show there's enough of a business there to justify going to the real App Store.