you can't exactly ignore/reduce combo-for-combo crushing vs crushed combos because remember the weight of the 50% will also effect the overall equity. so think of it in the extreme.... say you had 1000 combos where we crush them and 1000 combos where they crush us, that will average out to 50% as you say, but we can't simply ignore it because then let's say we have 10 combos where we're slightly ahead at say 60/40 favorite... well those 10 combos at 60% will also average in to the other 2000 combos, but not so much that we can simply cancel out and ignore the other 2000 combos. In other words, if we do the averaging, the answer will still be close to 50% because of the sheer weight they hold with so many combos.
So you're right, the crushing and crushed combos will average out to 50%, and if there are only a few of those combos, you can sort of ignore them, but you can't completely ignore them as the number of crushing/crushed combos increases, the closer to 50% your overall equity will become.
So to use your example:
I crush: 13 combos
I am crushed: 15 combos
Slight advantage me: 2 combos
you can't cancel out and ignore the 13 "i crush" and 13 of the 15 "i am crushed" combos as they will average out to 50%, and those 26 combos will pull up the equity of the 2 extra "i am crushed" combos and weight down the equity of the 2 "slight advantage me" combos.
Try it out in pokerstove real quick. Here's a super simple example:
Player 1: 9c9d
Player 2: 8c8d
Stove this and see 9c9d has 82.628% and 8c8d has 17.372%
Now what if we added canceling out combos of AJ and KJ suited?
Player 1: 9c9d,AhJh,KsJs
Player 2: 8c8d,AsJs,KhJh
Even though the 2 AJ and KJ combos of each player would be lumped in the buckets and seemingly "cancel out" in reality they don't as you can see by the new equities (try it out).
So what you've done is shown that TUPAC method isn't fool proof for every example (I believe I stated that in the vid, i hope so lol)... but the important thing is that IN PRACTICE, with many more combos, the inaccuracy we've shown here with very contrived examples doesn't tend to hurt you to this degree. Basically what happens is that the more combos you're canceling out (as a % of the total # of combos we're looking at) the more this inaccuracy will effect the estimate. That makes sense right? ... in the 99,AJ,KJ vs 88,AJ,KJ case we were looking at 2 combos out of 3 combos for each player that were being "canceled" and we noticed a dramatic effect. In the first example I gave with 2000 combos being canceled, that represented a high % of the total number of combos, and therefore a huge inaccuracy occurs. In practice, it tends to not be so dramatic (as shown in the vid).
I hope that makes sense.
WoT