The HM did mention those kind of examples at the open day we attended - we were also 'treated' to a DJ-ing set by one of the students and mention of one of the children excelling at the Maths Olympiads.
I think that most London schools of that calibre have similar examples (maybe in different disciplines) that they can roll out - SHS is well known for Olympic potentials, Harrodian usually has quite a few child actors / signed musicians... Not to mention other more 'academically selective' (sorry, I do not like the term, but useful as a shorthand). What I find interesting if that Emanuel seems to be one, out of the schools we visited (we ended up viewing 10) keener to make a point of it.
To be honest, it leaves me quite cold ...my DD does not fall in that category and, ultimately, I am more interested in what the school can do for her rather than whether there is scope for prodigies (some of which had focused on their passion / hobby / talent well before joining Emanuel) to study in Emanuel.