Today "competent" means licensed by the state. Not that any non surveyor county engineer should ever want to be in responsible charge of work outside their ability, but I've heard rumors... :)
This would also seem to indicate to me that a PLS is required in every county road engineer's office across the state (either as employee or consultant). They can't do what the law requires them to do without one (the way I read the history anyway).
Again, based on this history, and the laws cited therein, when the 1936 and before laws were written, no one contemplated that the County Surveyor/Engineer/Road Engineer wouldn't be a "competent surveyor".