I think i may be on to why this is happening...
i've been doing some tests and taking it one step at a time... also, redid the entire rigging (managed to find a way to save the animation data but that was because i created an identical set of bones and just constrained them positionally and rotationally to the old rig... then extracted the position and rotation data and reapplied it on a new layer and then collapsed it back after deleting the old rig... this was hairy and i'm still not certain that i'm typing the process up exactly)
but, i think when it comes to handling animations, only one layer is allowed to be set to a particular animation sequence, regardless as to how you've told it to behave (such as only animate the upper torso, lower torso, etc.)
going to do some more testing to confirm this and to figure out more about it... but, if it is confirmed that only one layer per animation set, i wonder if there are any resources that state this that i (and maybe another person) may be overlooking or if it's just not stated, it ought to be.... still testing to confirm though.
NOTE and UPDATE... yes, i have confirmed that even if a FSM is trying to access a layer itself, the animation data can only hold one layer value across the entire game as far as i have been able to figure. next step will be to take the animations i want to give two separate layers to is to just add in additional animations in the animator in the inspector and just tell it to use it separately... i'll update to see if that has resolved the issue.