In a related matter, what would happen if you connected a FF backwards? Would it still filter gas or would it allow the gas to pass through unfiltered? I know some vehicles are set up so you cannot hook them up backwards. In some GM cars, you caeasily hook the FF up either way....... I have pulled off fuel filters and had blackish gasoline pour out. It looked like Pepsi Cola.
I'd think the media area is the same. We are talking about the two sides of the same sheet of paper folded up.
I'd worry about the pressure ripping the media, because the assembly is not designed to support reverse flow / pressure.
Some fuel filters have a check valve in them to stop the flow of fuel from the engine and the line back to the tank after the car has been shut off so installing it backwards would not allow the car to start. (This is found on older model cars usually)
Normal (external from the tank) filters usually will work either way and work fine, but will clog up faster as mentioned above because the gas has less media surface to pass through if installed backwards.
They usually always print an arrow on the filter to show you which way the flow is, or they put different sized ends or connectors to stop "backwards" installations.
It's just a filter element in a can. I cut my Xterra's open and found very fine particles(not many just a hair(not from the cutting, different color and it wasn't metal). I took a razor and scraped against the filter media and brown sludgy/boogery residue was on the blade.
5 years, 35k miles, I think it was due for the Filter change. Filter didn't age well either, taking it off it was a solid rust ball except where the bracket wrapped around it.