I bet 90% of all fishing trips have less than 4 hrs of "concentrated" fishing time...
If I am in a kayak and I have to paddle more than fish and I am on the water for 7 hrs I guess that wasn't a fishing trip?
It should be from the time you touch a rod till you put it back in the garage. And it shouldn't be qualified by time. The amount of time spent is worth noting because an overnight 36 hr event can't be put in the same category as a solid 4 hrs at sun-up.
but the shorter trips most people do to "go fishing" shouldn't be discounted because of the amount of time spent with a line in the water.