I can not see why a business cant blow cavity insulation into the wall because it has not been repointed
Apparently (and so far two firms have told me this) - if the rakeout is too deep then water 'can' sit on the ledge made by the top edge of the brick, soak into the mortar, make the insulation wet and then (because the cavity insulation has filled the cavity and bridged what was a vapour barrier) make the interior walls damp & mouldy.. there's quite a few pages on t'interwebs about it being a problem in certain houses.
Mind, having said that, there are a couple of spots where I suspect I could poke a stick all the way into the cavity

Thanks for the link Entwood, btw

And Phil - the architect who designed these houses added some very "interesting" 'design' features.. like random areas that are rendered block surrounded by the rest of the brick, and the top four courses (or so) of brick aren't actually brick but rather single skin block work rendered on the outside so the cavity stops about 9" short of the top of the house. Very odd..