I have had about 5 hypnopompic hallucinations in my life (when waking up), and only one of them seemed real enough to scare the s#$% out of me, and was definitely not human by appearance.

Sleep insomnia can make normal people psychotic and prone to 'seeing things'. There were experiments done on 'normal/non-psychotics' under conditions of pure isolation and sleep deprivation, which led them to hallucinate and lose sense of perception. I have heard (I think it was David Eagleman) that the reason people dream at night is because that lets daytime-active mammals keep their visual cortex in use 24/7, and therefore not in competition with the other senses that would compete for brain growth while asleep. For people with abnormal conditions, like schizophrenia, I would say sleep is the number 1 factor impacting a 'normal healthy' person (meaning without substance abuse/addiction complications).

Shadows and low light conditions are the main stage for any illusion of the mind, with the whole 'we were designed to be watchful of tigers in the jungle' (rather safe>than sorry) metaphor.

I am convinced that auditory events are driven by suppressed stress and anxiety. Social circumstances govern internal thought processes.
Example: If you lived in the setting of 1984, then you would probably vent incoherent subconscious stress in the form of auditory hallucinations.
In your case, a xyz occurrence (job manager whining) can become a stressor with automatic responses in the subconscious.
And that might be vented when work ends or begins, in conjunction with a break from a routine/repetitive pattern.
I am guessing here, but this gives you an idea of what to ask or research about.