If you took 300 regular people, sent 100 to a school that trains "tma" and 100 to a school that trains MMA or even some other combat sport (wrestling, boxing, Muay Thai, BJJ), and then 100 who don't train at all as a control. The two groups who train both train 3 nights each week for 90 minutes. After a year, how do you think the three groups would fare in a fight? To be clear, I'm not talking about professional athletes or elite athletes or even people who are athletically inclined.
MMA is a training model. The difference in the training model is exactly what DB is pointing to. To say that MMA is an extension of TMA is a copout, like when Someone brags about how their cousin is successful, implying that they are also successful by proxy, or that they could also be successful if they wanted to be, while dismissing the hard work involved with success. Take the doctor example. A guy who works 80 hours at the hospital isn't going to become a great martial artist. Probably developing some real skill as a doctor, though. That person is making a choice.