For completeness, I repeat the explanation from the other thread here:
It would be bad, indeed if the cutoff and other sound parameter knobs were locked out, but of course they never are since they're dedicated single function knobs. The Amount knob is not a dedicated knob though. It is a context sensitive knob used for mod matrix editing, MID channel setting and sequencer editing.
The Amount knob is just like the parameter knobs used in context with the menu as found on many synths. Thus the Settings, Sequencer and Mod Matrix are different contexts that need to "own" the Amount knob - it's not meant as a performance function, although you can use it that way when the context is the the Matrix' Mods mode.
I agree that it would be handy if it worked when the Ribbon and Morphee pages are shown, since you may want to adjust a mod amount while auditioning a certain Ribbon and Morphee positions. I have submitted this suggestion on the internal testing forum.