CPX is listed in the "MC9S08Q8 MCU Series Reference Manual, Rev 3" as a valid instruction - lists the core as S08CPUV4.
But CodeWarrior says that instruction is only for the RS08.
If the reference manual is wrong, that would be a very serious documentation error.
If Codwarrior (10.0) is wrong it seems to not want to let me change to RS08 instruction set.