When I went to the Florida DMV in Clay county, Green Cove Springs, to change my plates over. I brought my truck and trailer. The inspector from the DMV went out to the parking lot and just checked the vin of the truck. He did not look at the trailer. I was surprised, but he said it was not necessary. They used the vin number of the trailer from the tile.
That was my experience. This is Florida, go figure.