FK Control Rig in sequencer disables Morph targets

Hi. When I try to add an FK Conrol Rig in sequencer on top of my animated head with Morph Targets, putting it in additive mode keeps only bones animation and morphs stop working, tweaking the value doesn’t do a thing. If I put to absolete mode, then I can change values and they work. Is it a bug or something else needs to be done?
*I don’t want to bake the animation to the Control Rig since it’s too many frames, and I just want to add few head rotations.
Thanks