OK, so they're "disclosed" in the sense that "the information (in packet form) is released onto a public network". But that's potential discovery if someone is paying very close attention. And the point of a zero-day is that nobody's paying attention to that specifically, because nobody knows to do so yet. So, yes, somebody could have a packet capture of it, along with a billion other packets.

So you're using "disclosure" here in a very restricted sense. It more normally means something more like "sending an email to the vendor" or "making a press release".