Ask HN: How much details of the advanced technology is hidden from the public

So it's clear that for military applications, a lot is hidden for security purposes... and also in general for industry because at the end of the day it is more the "how you actually do it" than "knowing how to do it which is important".

I was mostly thinking of this because of Elon Musk's comment "having the exposure to the latest AI improvements, i'm very worried".

How far do you think some AI guys can go without the general public can know ? Do you think compagnies like deepmind / openai are showing off only like 10% of what they are actually able to do while being way ahead, like "just enough" to get the best researchers apply ... ?