The first confirmed cases were in Wuhan, and right now, the state of science is that started either in Wuhan or near Wuhan. It's complicated science because where antibodies were found is still just one datapoint, a precursor can have the same molecular structure on the virus surface, so similar or exactly the same antibodies. Meaning since the discussed proCoV2 was only three base pairs away, it could be producing the same antibodies, be widespread, infect, even kill people, yet not be COVID-19.
The problem that the Chinese political system doesn't promote open academic discussion - that the virus is political - doesn't help either.
No, it's the conclusion of the paper cited in your source. The supposed proCoV2 is 3 base pairs away from Wuhan-1, and is 1100 base pairs away from other human-infecting SARS strains.
Basically there was another similar virus that had the same spike proteins - if you remember the photos, the virus is a spiked ball, the antibodies bond to the spikes. It was a precursor to the Wuhan strain, so basically the fact that there were antibodies in Italy before the Wuhan outbreak just means that similar shit was going around the world before, but not the same shit.
https://par.nsf.gov/servlets/purl/10287595
I haven't said anything about labs. Nobody treats the lab theory as a "proven fact". But it is a proven fact that the specific strain that got dubbed COVID-19 first appeared in the general vicinity of Wuhan.