I think it's good that a topic has been added on Mumsnet about this, if only so parents with supposedly "G&T" kids can talk about it, cos it sure as hell is difficult to in RL (the reaction on here gave a taster).
I think the label is crap too, but while it's being used in the education system, then it needs to be discussed.
From my own experience as a teacher in the state sector, and now as a parent, quite a lot of childrens "gifts" and "talents" can be overlooked, although they might be unearthed by chance whilst trundling along the National Curriculum Railway, passing through the stations of KS1 and KS2 sats.
We don't usually cover formal musical notation in Y1, but one day, early in the year, I showed my class a simple piece of music, and then I played it on a small glockenspiel. I let children take turns having a go on the glockenspiels I had set up. Most were merrily bashing away, role playing what I had shown them. But I could hear something faintly musical above the din. One of the children was actually reading the music on the overhead projector and playing perfectly!
She was only just 5, so I assumed she must have been having some kind of private music lessons. Anyway, talked to her Mum that afternoon and no, wasn't having lessons, never been exposed to notation before etc etc. I'd have expected this gift to have surfaced perhaps in Maths, but it hadn't so far.
Anyway, she started violin lessons through school and was going great guns. Interestingly her maths did then shoot ahead ability wise.
It was really only a chance discovery though - if I'd stuck rigidly to the curriculum plan I was following (which we were required to do as teachers), the we would have been none the wiser.