Hey! if you are referring to the Point of Service App listed at the beginning of https://docs.btcpayserver.org/Apps/ as stated on the docs on point 7:
Click View App to view your PoS (Your customers can access the PoS through that link).
The answer to your question is yes, they need a Tor browser. The problem is that this is not common on normal users.
I know that following the docs on creating a reverse proxy to Tor is not easy if you are not a developer. I can give you a hand on that if you wanted and test if it works for you.
Let me know if this helps.