I believe the rule reads "under control of the owner at all times." not "on a leash at all times". The OP Dog Catcher acknowledged the difference when he watched owners with dogs off-leash at the park. He could tell which dogs were under control.

It appears both you and the OP dog catcher who has this special ability are incorrect.  Given the law below was posted in this same discussion I'm not sure why you missed it. Give a copy to the dog catcher.

Laws of Worcester County, Maryland

§ PS 2-101. General provisions.

(s)Dogs required to be on leash. In any area described as a leash area in Subsection (t) hereof, it shall be unlawful for any person, or guest of such person, to knowingly, unknowingly, inadvertently, or intentionally permit a dog owned or harbored by him to walk, crawl, or run in any location other than the property of such person unless such dog is attached to a leash.

(t)Leash areas. Leash areas may be designated by law or resolution. The following are leash areas:

(1)Ocean Pines Area. All that property located in the Third Tax District of Worcester County, Maryland bound on the northwest by Beauchamp Road, the north and northeast by the St. Martin's River, on the southeast by the southeasterly line of the Ocean Pines Subdivision and on the southwest by MD Route 589.