Sump before the two, sump after. See if more moisture shows up. Repeated sumpings give a good idea of what may be being trapped elsewhere. Again, such individuals are being cautious, and knowing the limitations of their aircraft. There's a lot to be said for that.
Airplanes are mechanical objects, subject to imperfections and faults.
Pilots, by the nature of their calling, are about learning those faults and dealing with them. I am aware of the limitations of the systems in the airplanes I fly, and take measures to account for them. The pilot should read the maintenance manual and understand what the airplane is about. Systems knowlede, and an understanding of the limitations, is important. Two years ago I was on the field to perform some maintenance on transient aircraft there, and noted two emergency landings by their students which tied up the runway and caused a scene.