23andme does just weighting your matches with its algorithm for people which gave the location of their grandparents. This means if there are no matches for your in a region which gave away the location of their grandparents, you don't get it, even if you are 100 percent from that location. On the other hand, if relatives of yours moved to another place and are, let's say half Italian-half French, living in Brittany, you get that region. For me its e.g. Berlin. I have no known ancestry from the city, highly unlikely any of my German ancestors came from Berlin in the last 300 years, yet I do get it, simply because distant relatives of mine moved to the capital.
I didn't knew that myself, but a user on Anthrogenica showed it to me, you just have to look into the source code.
This is an example:
So I have 3 genetic relatives from Hessen, with 5 Hessian grandparents in total. So not that much, but something.
For your case, let's just assume a relative from Italy moved to France, had many children, so you get even more than one match from the department, et voil�!
Doesn't mean you can't have real ancestry from the region, but it could be very well gone in the other direction. Like I know from surname data that between various people and Germans there was so much reciprocal gene flow, that its hard to say which segment was brought by whom, by the Germans or the other side.
You can check for surnames on this site for example:
https://forebears.io/
I found two surnames, one rather rare, the other extremely rare, in other populations and regions from which I have no recent ancestry, obviously because one of the relatives of my ancestors was a trader or whatnot and moved into this country. In one case the surname is now more common in the foreign region in which not too many Germans were living at any time, than in all of Germany. So if I would get from 23andme a similarity for that region, I know why.
A fairly common Italian surname is Rizzo, if you look at the forebears map:
https://forebears.io/surnames/rizzo
There could be some clusters due to Italian migrants which moved there generations ago. Just in case you don't have any ancestry from the region, proven by your record and matches, this could be the explanation. Undertested regions won't appear in 23andme, because no testers = no matches = no ancestral region.