This anon is right.
I did some digging, and found that 256 bit keys are used for UP TO Top Secret data. So basic Classified to Top Secret will use 256 bit keys.
https://www.stigviewer.com/stig/application_security_and_development/2017-03-20/finding/V-70189
If indeed Q has given us enough to unlock the 40k foot classified data, then this should be a priority for work.