GRX derailleur in the picture, Ultegra RX in the specs.
Anyway, the GRX chainline change only really affects the GRX double crankset, since you need the accompanied GRX front derailleur to make it work. Using the 1x GRX rear derailleur with a non-GRX 1x crankset shouldn't be an issue.
That's a GRX derailleur in the picture though. Either the picture is wrong, or the description is off.
Weirdly the same mistake can be seen on Cannondale's own website:
https://www.cannondale.com/en-nl/bikes/road/cyclocross/superx/superx-grx
GRX derailleur in the picture, Ultegra RX in the specs.
Anyway, the GRX chainline change only really affects the GRX double crankset, since you need the accompanied GRX front derailleur to make it work. Using the 1x GRX rear derailleur with a non-GRX 1x crankset shouldn't be an issue.