When any documentation eventually emerged, Apple not only intentionally confused readers as to the reasoning, but also lied, and not just a little lie, just outright lie.Basically, because the EU is making them open iOS to other app stores and other browsers (real ones, not veneers on top of Safari/UIWebKit), Apple is trying to keep people away from other app stores by getting rid of web apps that make it easy to get to things on the web from the home screen, like app stores and other browsers.
Apple is ruthless about choking off competition. They blocked Spotify app updates (and maybe still do) that linked to spotify.com simply because it was a site that sold service subscriptions, as commercial sites do. Putting aside that Spotify is bad for artists and willing to do harmful in its desperate bids to have its own monopoly somewhere, that's just blatantly tyrannical behavior on Apple's part. They've gotten much worse than Microsoft bundling IE with Windows.
I did sign that petition, but I gotta admit, I don't really have much hope that a trillion-dollar company can be stopped from just crushing competition with money. I still use an iPhone because the phone market has been locked to Apple or Google for a decade now.
Anyway, we don't really need any more "shit sucks, and it looks like there's nothing you can do" posts out on the Internet, so I'll stop here.