I really hate both the tag 'G&T' and the way it is referred to as a SN. I have a feeling that the terminology DG is referring to isn't 'SN' but SEN (as in Special Educational Need) which is different I think. At least I think of them as different.
The reason I don't like the tag 'G&T' is partly because it describes a child as 'being their ability'. And I also find it a bit weird being a % of a peer group, because you could change peer group and then find you are no longer G&T even though you ability is identical. I much prefer proper differentiated teaching, extending the more able, supporting the less able. My kids' school don't openly do G&T, but they do have a massive spectrum of children, both in terms of ability and also backgrounds, and a higher than average intake of children with SN. But they all seem to be catered for educationally. (It is a state primary btw, but one that doesn't bother too much about govt hoops, so concentrates on the children).
Also, as a teacher, albeit a music one, I think there are very very few children who I have come across who I would say were gifted. 'Clever' children can often do well at something like the piano, without being gifted, especially to begin with. But I'm not sure you can begin to tell who is 'gifted' until later on, when the musicianship begins to come through. So a child can get through the early grades with high marks, flying through them, but actually not be talented at music, but be a bright child. In 12 years of teaching I've probably taught 1 or possibly 2 'gifted' children. But I have taught many whose parents (and a school going on a top 5-10%) would describe their children as such.
I know there are genuinely 'gifted' children. But I don't think these few are the many described by the G&T tag.