That's odd to include magnetic sensors as degrees of freedom; those are dependent variables whereas I expect if I have 9 d.o.f. (degrees of freedom) then I have 9 servos I can control, with orthogonality. I expect a linear basis in common; if someone says saw suction counted, I'd have to call that bogus, though it could easily occupy the same control loop hardware.
Anything further merely defines those servos; whether it's rotary, angular, extension, grip pressure, grossly limited or not, etc. just clarify what's been constructed on the 9 axes available. There's no reason to expect x,y,z and the first and second derivatives of them; or simply the fist derivatives and rho/theta/phi angle, would have any cardinality without the descriptive data necessary to form the Hermetian of those variables.