Yes, but how do you think X app will implement payments? probably linking banks or cards in the account, no? How to makebpossible to send and receive fiat between users from different countries? UMA helps here I think.
Discussion
Sure, UMA could help. Strike uses Bitcoin rails and partnerships with other Bitcoin companies to accomplish global payments. Both are KYC routes.
All I'm saying is that UMA adds a complicated layer that doesn't need to exist.