No it's very likely in fact.

iPhone has been around for 15 years so there almost isn't a person on this planet who doesn't know (a) what it is, (b) what the competition is and (c) whether it's a right fit for them.

So if you're surveying existing users you're talking to people who knew before they purchased the iPhone that it was going to be a suitable fit for them. So of course the survey is going to be highly biased in favour of a positive rating.

People buy things all the time that are not a perfect fit, just the best they are able to get at that time. Or they are forced into it for other reason.

99% is not possible. Nothing on Earth has a 99% satisfaction rating - not even breathing.

It seems very obvious to me that a 99% satisfaction rating for an electronics product is extremely unlikely, even given the factors that you noted. Not impossible like the other poster is indicating, obviously it's impossible to prove that claim, but very unlikely.

If you reflect on it and genuinely believe that 99% seems realistic and even "very likely", well, we'll have to agree to disagree.