Based on the fact that it measured 3.11-3.14 by those who ran the course and posted it to Strava, I think it’s safe to say the course is not short.
To me this proves the course is short. If the course is actually 5k then the gps readings should be longer than that. You should be seeing almost everyone with around 3.2 if it is actually 5k. Since they are getting right around the correct measurement, this proves that the course is short. They probably measured it so that it would give the correct measurement based on GPS which always leaves the course short. There are too many people that think GPS gives very accurate measurements. GPS is great and gives a great approximation of distance. But it is not accurate enough to measure a race course if you care about the actual distance. If you are ok with being "good enough" or "close enough" then it is great. And there is nothing wrong with that. But there are way too many people that get all worked up over XC times. The times mean nothing. There is no such thing as fastest high school XC times. The vast majority of courses used across the country are not actually 5k. Just ignore the times and pay attention to who beats who.
Not true GPS technology has come a long way. And if you are a good runner or smart runner who can run tangents well you will not be much over the certified distance for road races. Nearly every local charity 5k in my town uses USATF CERTIFIED courses and even in my hobby jogging state I never measure more than 3.14-3.15. good try though keep the hate flowing!