i have worked full-time at 6 different companies in engineering and management roles (admittedly none larger than ~300-500 people) and this wasn't the case for anyone at any of them, and have also never heard anecdotes from people in my life in general about this happening to them.

i don't not-believe you, but I would be super surprised if the 80% figure is accurate

the more common thing i've seen time and again is someone giving two week notice and then being told to not bother with the last two weeks (and not getting paid for it either). after one of my employers did this to a coworker i liked who was relying on that final paycheck for rent, i quit a couple months later with 0 notice "because it seems like you guys don't do 2 week notice here". I got threatened with a baseless lawsuit for that cheeky stunt and they abused DMCA claims on my consulting website to try to get it taken down