Growing up in a vocabulary-rich home, where reading is modelled and books available, puts you at a huge advantage, yes
Of course its not a bad thing but it will not in plant intelligence! It will not make a brain suitable to pass the 11+ .
I know, I was one of those dc, with a Father quoting long tracks of Shakespeare, Milton, reading me Macaulay Lays of Ancient Rome at aged 5.
It did not make me 11+ material. Yes I know this is anecdote but I am positive my brain is similar make up to other brains and will not grow, and become more intelligent by having books in house or well read parents.
Ditto the comp problem you like to ignore
Ha! Yes indeed.
The second option is a very unpalatable one and not many people have the hutzpah to express it openly
I always feel this is what you want posters to do, to come out and be open about social bubbles, keeping Dc away from what YOU call hoy poly, but I am afraid there are myriads of reasons why people choose G or P, and its oft been written on all these threads, people with really painful stories, and why they want something different and its all ignored because YOU cant shoe horn what they say into your narrow view that the only reasons people send dc G or P is to keep them away from knuckle draggers and chair throwers which are two phrases YOU keep bringing up.