Exxon mobil and Apple Pay cash back

Just got Apple Card and trying to learn my way around. Exxon Mobil is "partner" with Apple Card and purchases receive 3% cash back. I use an Exxon Mobil app to buy gas at Exxon Mobil On The Run stations in St. Louis. I added the Apple Card as the pay source on the EM app but only received 1%. Does this mean that I have to use Apple Pay to make the purchase to get the 3%? Or that Exxon Mobil On The Run stations aren't Exxon Mobil to Apple? Or something else? Thanks for any help.

[Re-Titled by Moderator]