In a nation that includes, amongst other cities, New York City, this is extremely unlikely.
New York was famously segregated by Robert Moses. It’s up there on the list due to being a welcoming and diverse destination today, but those policies of the past can be felt today, long after they are gone.
It's worth taking a look at their methodology and how they're measuring diversity. Notably, NYC ranks much higher than Houston for cultural diversity (#5 vs #28 for Houston).
But the fact that Houston is even in the list in the first place is the interesting part. Whether it beats NYC or not is sorta not the most important part of my comment.
It seems the Forrest might have been missed for the trees. (I don’t feel like you understood or validated what I said, whether you disagree with the precise methodology or not)