After the possibility of traffic violations the chance of being reported for ´illegal camping´ is the second most likely offence for the motorhome user in Spain.
Stopping overnight to sleep in your motorhome isn´t in itself an offence in the majority of Spain as long as the passengers stay within the vehicle and no activity takes place outside the perimeter of the vehicle.
That´s no table and chairs, washing lines etc. Also that the time spent there isn´t abused. I guess what there are really saying is that it´s ok to stop, park and sleep overnight but not to set up camp.
A lot of the reports that take place are by campsite owners putting pressure on the authorities to stop the practice of outside campsite stays. Which I can fully understand as campsites in Spain have strict regulations about the facilities they provide, no tents in fields or stays without all the necessities are allowed, making the running of a campsite very expensive.