Maybe a transient glitch? I see it in the Android app under the Membership tab, in the Benefits section (either swipe to find the airline fee credit, or tap "View All")

I also see it on the website, though it's more hidden -- you have to find the page that shows the full list of benefits: click "Rewards & Benefits" in the top navbar -- this loads a page that mentions the airline fee credit but not the selected airline; however if you click "Benefits" in the secondary navbar on this page, or click where it says "View All Card Benefits" this loads another page. This 2nd page may show the credit usage in "Benefits Activity" at the top without the airline, but the "All Benefits" section scrolling further down does have a banner with the selected airline.

But it's also possible that from time to time the website fails to fully load the info.