My opinion is that the G&T thing is misguided. Agree with some posts above that its really quite rare. IME gifted and talented children tend to be very very annoyingly self conscious and precocious and I get peeved that their parents don't try to teach them how to behave better and not be such big heads.
Also, they burn out quickly. For example, they get through school and then when they leave home for university they fall by the wayside, often finding that their peers at Oxbridge or wherever are just as clever and have caught them up, plus they don't have the psychological hang ups from years of special labelling.
I have never read the threads about gifted and talented children. I think it is a load of bull. This is because I was one, so I feel entitled to say it, having experienced it. Much better to just be treated normally and not have such parental pride/pressure/expectations heaped on you. Anyway, in the old days, such children were just treated normally and just read a lot more proper literature very early on. Which teaches you so many things you don't get in a classroom or mentoring situation: instant and private access to the finest minds and thoughts.
Often those who were gifted at maths seemed be almost at the end of the SN spectrum and slightly autistic. And before people start getting offended, this is the case with a very close friend of mine who did Maths at Cambridge, and also with DH who is very mathmo but a bit "special". Also, because he was so talented at maths and science, he went right through the highest levels of the education system without anyone noticing that he is totally dyslexic.