It isn't that simple. Travel agencies often pass through the booking to the airline, and the airline generates the card transaction, which may trigger the bonus. 3X for airfare is carried forward from Premier Rewards Gold. Here is a discussion:
PRG and BGR Airfare Triple Points via OTA?
Hello Mia,
The last post was from 2015. It would be great if we have a dp from 2018 especially after AMEX revamped their card.