Google Pay for online payments is more akin to Paypal. (Google processes the transaction as a traditional online payment, using the credit card number you enter in off the card itself)

Apple Pay for online payment interfaces with the secure enclave on a supported device to be able to do the real-time challenge token exchange, and is processed against the device account number from secure enclave.

Despite having similar sounding names and appearing to operate similarly, they are very different in how the transaction itself is processed.