Employees of parks, storage yards, repair shops, etc. have no reason to see your driver's license and know what type of license you have. They are not in the business of enforcing driver's licensing laws, and might only get involved to interfere if you're trying to do something patently unsafe.
The DMV (at some level) presumably does know about and know the statute. The DMV handbook, however, is not infallible, and was written or edited by someone who didn't read the particular statute carefully, or who was slightly careless with their use of language. It doesn't take too much imagination to see how "not exceeding x" could become "under x" without someone noticing that they aren't precisely the same thing mathematically speaking.
I honestly believe you're overthinking this, and worrying excessively. Any possible legal liability, beyond any fines and fees for lacking the proper class of license which would not apply as you'd be properly licensed, would be covered by your liability insurance; that's basically why you have insurance.
