i have seen things like this before and have read several books where they have suggested growing more than one tree in one hole..however, I do find that unless you really are cramped for vertical space it seems a little silly to prune the trees so short..
if you are putting in dwarfs they should be small enough to reach easily from the ground or from a small ladder (i like the folding ladders with the platform steps that lock into position)..
I understand what he is doing and it might work out well for people with very limited space..
Bloom where you are planted.
i want to try such things with "standard" rootstocks so as to potentially have a larger root mass in relation to the size of the tree up top. im experimenting with it now, but its much to early to give a diagnosis.