Re: I think I disagree, but I’m not sure…
> "No, but you *are* stopping me preventing it"
No, we're not. Apple isn't going to remove the walled garden in its entirety just like that. All we are asking for is that a gate is installed into that wall. Apple will lock that gate by default (and that's fine), but there has to be a way to unlock it if you so wish.
> "I want to know with 100% certainty that if she downloads “the Barclays app” from the App Store, she isn’t downloading a scam."
Never going to happen, not least because scam apps do make it past the Apple/Google police and onto the official stores from time-to-time anyway. Saying that however, even with a relaxation in rules, if you mother goes to the App store and downloads the Barclays app, she is still 100% getting an app that has been approved by Apple because the app is still coming from within Apple's walled garden. I'm sure Apple can add the ability to PIN/password protect an "enable sideloading" option, so it'd be perfectly possible and simple to lock a device to App-Store only installs. They'd have to do this anyway so that parents could lock their kid's devices to avoid the ability to accidentally sideload malware.
> "The question is - legally, what gives you the right to force a company who wants to provide the service I want, and I want that service, to stop doing so?"
Simple, competition law. For small companies, this isn't an issue, but as companies grow larger and their power and influence grows, so too does the scrutiny that they are subjected to - particularly around abusing their position for their own gain. As the largest phone-maker in the world (they overtook Samsung this year), Apple is a large and powerful company. Developers that write apps for mobile devices effectively *have* to provide an iOS version unless they're willing to forego a significant section of the market and the sales that come with that. Because developers pretty-much have to support iOS to succeed, this means scrutiny to ensure Apple isn't abusing their position. The EU have decided that Apple is abusing its position, hence this ruling about opening up the platform to some degree.
TLDR: The walled garden isn't going to disappear and you will still be able to lock an iOS device to only work with the App Store if you so wish. However this shouldn't mean that everyone else with an Apple device has be subjected to Apple's whim and rules.