If the PoS supports tokens, it’ll use unique tokens for each payment. If the PoS doesn’t support tokens, the phone has a virtual credit card number linked to the real one, so if it does get stolen, you can just remove the card from your Google Wallet to deactivate it. Your real card number is never exposed.

Even then, credit card numbers on their own aren’t that useful anymore. Any online payment needs the CVC and PoS devices usually require chip or tap cards, which don’t use the number. On top of that, credit card companies have purchase price restrictions when using swipe because of the security risks vs chip (which is why most PoS devices don’t support swipe anymore).