Regardless of whether or not he is working traffic control, anytime a police vehicle is seen parked beside the road a Police Report is appropriate rather than a Hazard. So many cars pulled off the shoulder and dead cats get reported that many Hazard reports are given little concern. I try to be aware of where a stopped car is, just in case they decide to start moving again, but otherwise don't adjust my lane or rate of travel. I see a Police report I look to not only adjust my speed if needed, but also my lane so as to obey the Utah law similar to the one mentioned in TX about moving over and slowing down. Many drivers don't move over even when they can but many could if they knew in advance.
The idea isn't really to help people avoid getting tickets, it's for safety. Reporting an actual speed trap in operation advises people to slow down there (when the threat of a ticket exists) but it also advises people to be careful as, whether he is sitting gunning for people with radar or he has someone pulled off to the side, caution is advised. If he's sitting there he could need to pull out into traffic at any time, whether to deal with someone he's caught speeding, to respond to an accident call, to respond to a different call for his services, or to go home/go restock his donut supply.
If he has someone pulled over or is assisting a stranded motorist, it's a warning to be careful.
Any officer sitting beside the road should be reported, more for their safety than to help others avoid tickets. And any car in motion should not be reported as previously explained.