Most races I have run are smallish, local events with hundreds of entrants. Yesterday, I ran in an event with about 2500 people. With the SPR in mind, I tried to run as smartly as possible. For seven miles, it was too crowded to run the SPR. For the remainder of the race, after the crowd thinned out, I watched many people run all over the 30 foot wide roads - almost never running the shortest route.
If some of the entrants used a GPS that is accurate only to several meters and they ran willy-nilly over the course, I'm sure that the course was "too long".