Here is how it worked for me at one day;
I did PP positions from level 110 till 130 only using offensive positions. Before doing it, I filled my resource storage to the max. By hitting these positions, I did lose some serious amount of units, some positions had very low amount of losses while others were huge. Still I would get some ''decent'' payout from each position so it was basically pushing me to go more and more. At 130, the positions didn't go more they stopped. I was at debt yeah... what to do ? I picked position 112 with defensive troops this time and I got 13k mounted peltast and 2k phalax offensive.
Now was that worth it? Well considering that I converted all phalax units to cavarly, I'd say it's kinda worth it. I am still in debt of units number not calculating the actual def/off points. But I was satisfied to see my 3-4k def units get converted to horses. My offense on the other hand suffered a lot but I'm a defensive player mostly...
Then several days after that, I tried the tactic again but this time nope it doesn't work. Tried on all accounts but nothing. Always in debt and getting small units even tho my storage is full. I found it very suspicious. Then at one position I lost my units and failed to raid PP position. One bar from four was left at position strenght so I thought, let's try it with the forces I have left... Then bum, I get around 6k phalax payout at that exact same positions where Persians were weakened. So total 4k units profit which is meh. This was level 82 position tho.
Next days I tried on my different account the same thing. No profit from direct wins. So I tried this method from the above, lose around 2k phalax def units to position 82+ and leave it at 1 mark strenght. After I finished the position with what's left of it, I got 6k horses payload.
As you can see PP positions are very confusing and I cannot know exactly why it worked this way and why it even works in general like this. You seem to get bigger payloads if position was left at 1 strenght rather than finishing it on the first try...