Interesting and important question(s). I recall having this conversation several months ago on this forum. There is a qualitative difference between "spanking" as corporal punishment and "beating" as corporal punishment. The terms seem to imply a difference in severity. That difference is significant and may be even more significant depending on the meaning the child assigns to the punishment. What are the implications of that? We may be able to readily come to consensus that corporal punishment is not "necessary" for behavioral correction as much as it is (perhaps) efficient and (perhaps) effective at instilling fear and thus avoidance (extinction) of the behavior that was antecedent to receiving the punishment.
I wonder about the consequences related to saying yes to the question from the original poster "If a childhood spanking causes involuntary sexual effects or stimulation in a child, would that be categorized as a sexual abuse ACE?" I wonder both for the child/adult (to perceive that a loved one "accidentally (?) sexually abused" them and the caregiver (to be thus accused). It matters.
To the question: At this point, I think the value of parent educators and other "psychoeducators" might be elevated by teaching to raise awareness of such "involuntary" outcomes and the potential impact they may have on the child's psychology and development (IF there is sufficient data to identify those effects). Jane's sharing of "effective parenting" or positive parenting is well received.