Do you trust the dealer? Did the mechanic forget the filter or forget to reset the maintenance reminder? How does the truck track when to change the fuel filter? Is it purely off of miles? Does it include a calandar timer? Does it use sensors? Have you drained the filter to make sure it isn't filled with water?
I don't know much about your truck or engine, but I am the maintenance engineer for a very large fleet of diesel powered generator sets. We spend millions on preventive maintenance (PM) every year. I work to make sure my fleet has just enough of the right needed PM to ensure a reliable low maintenance life. I talk with engine and generator application engineers on a regular basis.
Those SMEs have shared the following. The fuel filter is essential to long engine life. Most engines today use a common rail fuel system with electronically controlled injectors and high pressure fuel pumps that can put out 30,000 PSI. For reference, water cutters cut rocks and steel with 30K to 100K PSI. Both the pumps and the injectors can be damaged by tiny particles and water. The particles can act like abrasives and wear metal inside the components. Too much water in the fuel can turn to steam in the injector and blow off the tips of the injectors. You want to protect the fuel system from wear for engine power, fuel economy and to control emissions.
Fuel filters capture the tiny particles and separate the water from the fuel. Filters can fill up with particles, eventually reducing fuel flow and pressure to the engine high pressure pump. Fuel filters also degrade with time. I suspect the over time degradation affects the water separating capability more than particle capture, but I've never asked.
I've asked about extending intervals and none of my OEMs like the idea. They push back hard and give me plenty of reasons to use their intervals. It's curious too because they could sell more replacement engines/parts if I wasn't doing enough PM. I think some of this reflects that we don't have affordable technology to determine the actual condition of the filter (condition based maintenance), so we change them before they reach a worst case failure. The filter is protecting the engine for the whole PM interval when continuously fed contaminated and water filled fuel, but what if the fuel is good quality, clean, and filtered prior to filling the tank. The OEM nor the engine really know which is the case they plan for the worst due to the high costs of failure. Oil change intervals are really problematic for this same reason. I reviewed oil analysis results in the 1990s and I saw recommended change intervals that were double or more of the hard oil change interval. The longer intervals reflected the engine condition and favorable environmental and operating conditions.