I literally just googled "Cover 0" and this was at the top (warning, it contains some words that may trigger you):
Cover 0 is a coverage scheme with zero deep defenders. This is an entirely man-to-man coverage shell that involves a heavy pass rush ‒ normally six or more defenders. Accordingly, Cover 0 is also called a “zero blitz.”
See, it simply means no one is deep.
You can deploy it with man-to-man, as you said.
Gasp - the word SHELL!
A heavy pass rush with 6 defenders....hmm, sounds like a BLITZ to me.
Maybe you've heard it called a zero blitz. Maybe it's just a thing you haven't been exposed to. Either way, yeah, calm down. LOL