i wasnt aware of that. my main worry is if the lens comes in bad condition with dents or scratches. I guess there is no way to know that before buyingWhat do you mean by legit? EBay has a very strong buyer protection policy, so you can simply return the item if there are any issues. Even if the buyer states "no returns" you can open a not as described claim if there is an issue and eBay will rule in the favor of the buyer 99.999% of the time.
The only thing I would worry about with eBay is if you're buying from out of the country you may not get a proper warranty, I'm not sure how Panasonic handles international warranties.
Some items on eBay may be new but removed from kits, so it will come without the retail box, but generally this is clearly stated in the listing.