If that's the case - No.
Shadow guard actually can learn ALL techniques, as their force users come from a various medley of backgrounds. We have Shapers of Kro Var, ex Jedi, ex Sith, Fallanssi, Dathomiri witches, Zeison Sha, Keetael, and the Matukai -- you might even be unaware of a Warden of the Sky in the mix --- remember.. these are folk who have been hired from various different backgrounds with a vast array of skills and techniques learned in the past that they can share and train to others.
The thing about the shadowguard is this... they are always constantly bringing back new techniques to use, we are not limited by a Force code or mandate of the Sith or Jedi Order per say -- other than a contract. ShadowGuard are always constantly bringing back anything they find during their missions, be it new techniques, holocrons, ancient tech...
In fact, that is one of the main missions some ShadowGuard do.