1) It's fair to let people choose a different app (I know many people really want this on iOS), but I think his complaint is valid. There are many situations where it's completely unclear to a new user why they should use app X over Y for photo management/SMS/etc. To ask them before they've even used the app the first time nearly ensures they're not ready to make that decision. Sensible defaults and perhaps delaying the prompting until the device notices the user uses an alternate app a couple of times may be a better way to handle this.
3) Why should it matter if my HTC One came from a T-Mobile store or not? The fact that they behave differently (and especially that T-Mobile's support isn't prepared for that) is clearly an issue. I think the voicemail note is telling. How many people, upon buying a new phone, would think "I need to go download a special app to get my voicemail working"?
4) HTC took something that worked fine and made it more confusing. That's clearly a design mistake.
5) If something doesn't work reliably, that's a design issue. Especially if it used to work.
> But I stopped reading past that [...] I only saw "iOS is right" in some places.
That's not what I saw. Rorschach test for your preference for Android/iOS perhaps?