To me, it looks like they ran out of space to display all the benefits in the 3 big blocks per line format they chose. They would have had to make another line with only 1 big block on it (and a big empty space to the right of it) to show the $250 airline credit, and they chose appearance over information.

But isn't "appearance rather than information" the sum of most of the website overhauls that banks have been doing the past couple years (mostly seeming to want the website to look OK on mobile devices, they "wreck" it on desktop computers)?

If they'd chosen to show the benefits in bullet point text, then they could have any number of benefits listed. But since the went "form over function" to show them in 1/3 of a line big square blocks, they didn't want to have a leftover line with only 1 square block, so they left off a benefit to make it "look nice".