Yes, zaps themselves are public, but you're introducing a third party to see what you do with it afterwards when you dont have to.

You must not know how ecash works then. Anonymity sets are fractured up between different mints. And denominated tokens within each mint splits it further. That will never be as private as a single unified anonymity set.
https://image.nostr.build/2223442b69b3a383d66fe7f59824ad7364e9702f2f0b5354e69391a1738b36e1.jpg
https://docs.cashu.space/faq#general-safety-and-privacy-questions