I don’t know that 4oz gloves are the problem. Boxers have more brain damage if anything and they wear 10oz for their fights. Gloves protect the hands and wrists and your face from cuts I feel like
What's gonna matter most is how the athletes train, how hard they get hit in sparring. A very long professional career might be 30-50 fights, but that's thousands of hours of training. If you're spending much of that sparring hard, even if you don't get many concussions, the cte is going to build up
My thought was that since western boxing is limited to hands and standup, you’re going to go for headshots a lot more. You’re limited in your weapons. Muay Thai has a lot more options, and since punching scores less, you end up with a lot more shots to the body.
I only brought up the 4oz gloves in my original comment because I just don’t enjoy watching the style of lots of punching headshots as much. I feel like modern scoring and use of gloves that get through guards easily changes the style and encourages more punching to the face, which isn’t what I find artful in Muay Thai. My personal weapon of choice is going for knees.