It’s only US ‘person’ customers they ban (due to CRS standards and them not being set up to report accounts to HMRC).
And yes, gender-neutral titles would be easy, to me, it shows a rather out-of-touch management - like a typical legacy bank.
Like Monzo does? Yes, that’s great to me. Personally, I’m indifferent to being called Mx or no title. I know the older generations tend to like them, and I respect that as well… so it should be optional, and, ideally, a free text field.