Jimbo, I know how to check for cars at various sites.

It does not change much from location to location. Heck they even list a Mitsubishi Galant and they have not manufactured that car for a couple of years they also list their convert. as a Sebring (in Canada), which was renamed a couple of years ago to a 200. They list the Mustang as a convert in the US and they offer the 200as well and they have more of those than anything. And, yes, different countries do have different cars. They don't list every single car they carry, just the "x or similar". And, it is pretty obvious they don't update the list very often. You could ask your FIL where the car is registered. Easy enough to look at the license plate. As I said, Hertz now owns Dollar and Thrifty, they share cars, Hertz has VW's in their fleet and it is possible that a Passant is in that mix.
Since they do list the Altima as full size, it would not be a surprise to find that the Passant is also a full size.
I found these numbers for Dollar @MCO: (407) 583-8000 and (866) 434-2227, not sure if you used these or not.
As I said previously, have your FIL check his contract, it should list the car type/class, also have him check the license plate, that will tell you where it is registered (I know, that was obvious) and give the numbers I gave you a call.
As to "does he have a complaint", I cannot say. I can say if he is not happy, I am sure they will switch it out for something he likes. I am surprised he took it in the first place, I believe Dollar allows you to change to something in the same class if you don't like what they select for you.
Wish I could be more help. Have a great day.