Absolutely this.
It's not even a standards issue, for the outside world they're completely different email addresses. The fact that they happen to land on the same inbox for some providers is unrelated, it's just how that particular provider decided to handle all your different email accounts.
Yes! And if you have your own domain, you can just setup a *@example.com to be your one email address. And then you can give a different email address out anyway even without needing to go +. As you said each system can treat it differently.
