Exactly the right answer. I know these people. They use "diverse" as a synonym for "non white". But then it's also a trap, because the interviewer was correct: a roomful of Hispanics is not actually diverse, ethnically speaking. The correct answer would be use the question to showcase how you treat everyone as a unique and valued individual, regardless of race, ethnicity, etc. If they want to come back and say, but what about X, Y or Z ethnic groups, then at least they've had to expose their own narrow-minded view of diversity in the process, while you have had already taken the opportunity to tout something good about yourself.
” then at least they’ve had to expose their own narrow-minded view of diversity in the process,”
And that is proof to you that you don’t want to work there anyway! ;-)