Unless you add a Mastercard to your Google Pay account, because Google purchases Mastercard data directly for ad targeting purposes. So he's being very mislead

Unless you add a Mastercard to your Google Pay account, because Google purchases Mastercard data directly for ad targeting purposes. So he's being very misleading here, likely deliberately. They don't directly share it with the rest of Google, but indirectly your Google Pay data is still laundered through shady Mastercard deals to Google's ad behemoth anyway. Google Pay -> Data laundered through Mastercard -> Google Ads