My understanding of TMA is that it originated from Village defense. So the village is like a family unit that has it's method of hand to hand combat. Back then there would be disputes between villages would lead to fights. Fights could be as small as teens from my village going to your village to beat up another rival teen group. No different to how gangs work, were some people in one neighborhood don't like people from another neighborhood. When I lived in Baltimore, being from a specific neighbor could equate to "being on the wrong side of town." If people knew you from the wrong neighborhood then that would be a butt kicking for you. In the Philippines the martial arts systems are identified by location / village.
From what I can tell by researching other cultures. Tribal warfare and village warfare are a real thing back in the past and as a result. You would want to keep some fighting methods secret to your village and not shared with other village. You would also develop fighting techniques that would work against another villages strength. There would be cross pollination eventually either through friendships or fighting, but for the most part the villages are trying to out do the other. In terms of Martial Arts, there's a lot of stuff that doesn't make sense in Jow Ga until you use it against another system.
A good example is a technique that we have that punches off center in a series of jabs. If I use this technique on you and you stayed still in one spot then I would miss you with every punch. But if you bob and weave then the shots are going to lay you out. Jow Ga doesn't bob and weave, so by function the technique wasn't designed for Jow Ga vs Jow Ga. We have another technique that seems to be directed towards linear fighting systems like Wing Chun. I say Wing Chun because the more linear a person is, the more likely I can pull it off. I don't know anything more linear than Wing Chun
If we take a look a Wing Chun we being to see how Wing Chun exploits weaknesses in circular systems. Is Wing Chun Circular? Can Wing Chun fight against Wing Chun and win. Sure of course. I would never suggest that this was impossible. But from what I've seen time and time again and from my own experience is that TMA practitioners who use the techniques against other systems often have a deeper and better understanding of that technique than they would if they only used it in the context of System A vs System A.
But back to the point.
This is Wing Chun when you train Wing Chun vs other systems takes this shape. This is true for any system that does System A vs System B.
This Wing Chun when you train System A vs System A. It tends to take this shape. Again this is true for any system that does System A vs System A