At the end of the day I honestly can't see how keeping this secret improves security overall. Something'll give eventually. It might be in something protected by these modifications, it might not, you have no way of knowing, so it's not like Apple is actually winning anything by being protective of This One Specific Corner.
If anything releasing the modifications would carry significant weight and might even kick the tires sufficiently enough to see some coherent coordination and actual traction. I mean Apple clearly have the knowhow, what with LLVM and all!
:v