Yes, "microsleep" is brief periods of time where your brain shuts down or "sleeps" while you are conscious. It's enough to help sustain you through the very low sleep periods that seem to happen to most coming off Benzos.
I never understood how I could average 5 - 10 hours per week and yet never get sleepy or tired enough to nap or nod off behind the wheel.
It's amazing how well we can function on so little sleep. I looked back as some work I did at my place of employment during the worst of my WD insomnia and it was actually on par with work I did while sleeping "normally."
And to answer your question, yes, almost everyone gets more sleep than they believe they are getting. There were several times I was sure I did not sleep at all but my wife said I was snoring or breathing like I would when I sleep. That's why I qualify "zero nights" with no perceived sleep. Granted, even if there is unrecognized sleep, it's not a lot, but any sleep is always better than no sleep.
Time is the healer. Time will even out your sleep and it will slowly return, but is very UP and down. You could start to sleep OK for days, or weeks and think you are healed only to go back into poor sleep patterns for days or weeks. Eventually it all evens out.