I am deliberately not mentioning specifics. But the indications are there if you're looking in the right places.
First example: pilots from a particular community 'disappear' for months at a time. When they come back, they're unable to say where they have been or what they have been doing - i.e. they don't even bother with a cover story. In this particular case, the suspicion is that they are rotating in and out of TDYs to fly an optionally-manned platform. This may well be it:
https://theaviationist.com/2014/03/2...over-amarillo/
Second example: I am aware of recruitment into a black programme that is operational in nature and favours those who have been assigned to a small set of specific white world squadrons (i.e. these particular squadrons act as clearing houses into the programme). Recruitment into this programme has been active for a decade or more and these aircrew use cover stories.