Can confirm. "Zero day" means you've had zero days to patch. The term has been used this way since, IIRC, the late 1990s. See Phrack 53 for an example:
Tl;dr: it doesn't matter. A low-severity bug was found, and then was fixed.
I got yelled at once for using the word “cheap” to mean “inexpensive” once and wish you had been there with me.
From someone running a system, it doesn't matter if the vendor had 0 prior knowledge of the vuln or if they had made 25%, 50% or even 99% progress towards a patch. The point is there is still no patch available for the vulnerability and your only defense strategies are the same as if the vendor hadn't known at all, so it's still a 0day.