Hey all again. I hope nobody minds answering what is most likely a very novice question, but one that I couldn't find a clear answer for online. That is, why is the Franco-Belgian style considered most functional for classical music?

As I practice it, it is very difficult to maintain properly, along with a curved thumb and quickly fatigues my right hand. However, playing as the "little kid" style with the thumb underneath the frog, its much much easier for me. Also, mechanically, under the frog seems to have the advantage, as you have greater leverage over the pitch, yaw, and roll of the bow than in the traditional Franco-Belgian style. So, my real question is, "why is it considered bad to play with your thumb under the frog in classical music, not the fiddle style"? Is there an advanced technique that I haven't learned yet that requires the thumb in the traditional style?

I know other forum topics state that TUF hold is superior for most in fiddle playing but they say classical artists roll their eyes at it. It's not just a traditional elitist thing is it?