That may just be feeling and intention co-arising and co-ceasing together, or habit as was said above.The point of the thread was to figure ou whatt about pleasure made it so appealing and what about pain made it 'bad' as we know that we chase and avoid these two...but why?
And since you mentioned evolutionary biology, they may have been beings where those intentions would go in the opposite direction, but those beings are not in the same realm with us anymore. Who knows, maybe this is what hell is, you see pain, you go towards it and you have more pain ?
I think your dramatic examples of pain, torture, death are more difficult to investigate.
I have actually looked at smaller things and tried to compare pleasant feeling with painful feeling and found no significant difference between pleasure and pain.
Except that they arise together with the intention, impulse to move towards / away. And interestingly, the impulse has a pleasant/unpleasant feeling of it's own attached to it, maybe a feeling of confidence or doubt about the reaction we have.