This is an interesting study. Let me use this analogy...

I hold my pencil wrong. I can write fine. My script sucks but if I slow down and print people can read it fine. I've tried holding my pencil properly but I can't write worth a darn that way. I'm 33 years old now and have been holding my pencil wrong for 28 years.

I think how you hold your Tx is probably the same thing. Whether or not there is a right or a wrong way to do things is relative. If you've learned to fly with your thumbs and you're good at it there is no real reason to change. If you feel your control is somewhat lacking then maybe you could try pinching.

I learned to fly with my thumbs, but some old timers made me change to pinching. As I sit here now, though, I can't honesly say which method I use, but I fly real well. I think it's just a matter of preference.