I don't believe that that information is currently correct.

By my recollection, any territory with a morale below ~34% has a chance of spawning a unit of Insurgents. Keeping a friendly unit stationed in a location reduces the percent chance of insurgency occurring; however, the chance is only reduced to zero if there are multiple friendly units stationed in the same location, sufficient to mitigate the chance of insurgency completely.

The percent chance of insurgency can be found in the information tab found directly above the morale bar of a province with a morale of less than 34%.

My knowledge atm is not the best but I believe if morale is below 35% it is possible local resistance will spawn and fight and then take the province under Rogue State, this happened to me 2 days ago or yesterday can't remember which day but it happened

Any city with morale at 33% or lower can suffer from insurgencies. Stationing one or more units will reduce the chance.
You can see this and experiment with it by clicking on said cities‘ morale info.