The only thing we know for sure is that the van was titled to Gabby and registered in Gabby's name. That's what her father said, and I have no reason to doubt that he is more familiar with the situation than all sleuths except LE.
And the FBI said, on their original "Petito" website, that "she was traveling in a white 2021 Ford Transit van,
registered in her name, with Florida license plate QFTG03 and decorated with a variety of stickers on the rear." (BBM)
(link to the online cache can be found here:
FBI — Gabrielle Petito – Missing Person). Here's another source:
A Timeline of the Search for Gabrielle Petito and Brian Laundrie
The van had Florida plates. So Gabby registered the van to some address in Florida, whether it was the Laundrie's house, or whether it was some other Florida address.
If the Laundries insured the van through their business, they would have known for sure to whom it was registered (likewise JP would have known if he insured the van through his business).