With due respect, you are wrong.
hack
…
- (transitive, slang, computing) To hack into; to gain unauthorized access to (a computer system, e.g., a website, or network) by manipulating code
Hacking means gaining unauthorized access to a computer system by manipulating or exploiting its code.
Exactly what this is. Read the disclosure. What about your response doesn’t fit that?
They did not do it by manipulating code. This wasn’t the result of a code vulnerability. If you leave the door wide open with all your stuff out for the entire neighbourhood to see, you can’t claim you were “broken into”. Similarly, if you don’t secure your endpoints, you can’t claim you were “hacked”.
Lack of rate limiting is a code vulnerability if we are talking about an API endpoint.
Not that discussion makes any sense at all…
Also, “not securing” doesn’t mean much. Security is not a boolean. They probably have some controls, but they still have a gap in the lack of rate limiting.