I decided to run the game a few times and it seems that sometimes depending on the fight, if you hire mac to knock an opponent down, then quickly knock them down again without getting hit too much, there are small chances that they stay down after the second knock down. I managed to keep the 2nd guy and evil Wade down after the 2 knock downs one time, and then the next i only got the Devil to stay down

Thats the "meta" of the game. You can see this in the WR run and mine as well (I was to stupid to DL and upload mine to YT). Mac is the best helper in the game. You want to get him for every single battle you can afford him. Since there is no RNG manipulation known, its the most consistent method to quickly win fights, as it is pure RNG if you get a knock out.

The first knock down is hard-coded to NEVER be a knock out, so starting the fight with a guaranteed knock down from Mac saves you a lot of time. Especially as the opponent is on half HP after that as well.