I was thinking, while away from this thread, how differently we treat children who are gifted academically, and those who are talented in other fields.
(I will refer here to academics, music, dance and football, as those are things I have personal knowledge of)
If the OP had come and said ' I have two children who are showing great musical talent and play their instruments to a surprisingly high level for their ages - I'm looking for some groups and opportunities for them to be with other musicians of their age / ability' - the thread would have been as overflowing with support and ideas as the music thread on Extracurricular Activities always is. Nobody's first response would have been 'No, don't let them do any more music - it must all be about making friends with normal children.' There would have been an acceptance that children who do music well spend a lot of time doing it, and naturally make friends with the children they meet who have the same interest.
Similarly, if OP had said 'My DCs are showing great aptitude at ballet', she would have received advice about good local dance schools, junior associates etc - and again, there would have been an acceptance that a child who loves and is great at dance will spend many hours dancing, and socialising, with their dancing friends.
Same with football. IME when DS was part of a professional club's Academy, nobody said 'Don't play any extra football; spend that time making friends with non-footballing children'. It was all about what great friends he made within his various teams.
However, when it comes to academic ability, and children with interests that fall under the 'academic' banner - Maths, Science, Coding etc - somehow it is seen as 'wrong' for a child to spend any more time on it than they have to at school, and they mustn't join any clubs of that type, and they musn't seek to find others with the same interest because it is more valuable to 'meet a wide variety of people'.
Why it is different if a child's 'thing' is Maths or writing stories from if it is Music or Dance or Football?