The author of the review of these wheels wrote:
Three of these cyclists are running the wheels on their CX bikes (for gravel racing), such is their improved performance over stock CX wheelsets.
I asked in the comments section and the author replied:
The newer versions of these wheels with the 11 speed body (I believe any hub shell marked from D onwards is 11 speed compatible) work just fine with road or CX type cassettes. For example, two of my teammates are running various combinations of the SRAM 1170 cassette, in conjunction with a SRAM Red 22 drivetrain. I cannot speak for the older generation wheels, but perhaps one of those 3rd party cassettes that fit 11 gears into the space of 10 will work. Worst case scenario, call American Classic with your questions about which generation of wheel is specifically 11 speed compatible.
Guess I'll take his word for it and nice of him to reply.
The bike I'm looking at is a 2015 CAADX. It comes with Maddux CX 2.1 Disk wheels. Note sure how wide they are but they have Sammy Slick 38's on them.