Very interesting. Thank God our kids are fine.
It is weird thought how they spoke late.
I do recall early on how my DS did say one word but said it wrong, instead of Apple he said "Appen" and that was it, didn't speak at at until 2 and 1/2 about.
In the book "enstein syndrome" he suggests it could gifted kids have a higher standard and being perfectionists they don't want to make a mistake so therefore don't speak.
This is a possibility.