Funny you should post that question. I just got certified for waterbourne paint two months ago and that was part of the test.
First, never trust what a supplier or manufacturer tells you, yeah, that was on the test.
Use thinner on a piece of rag only, not wax or grease remover or mineral spirits, just thinner. If itís soluble or lifts then you must remove coating. Also, take a piece duct tape and firmly adhere it to the panel then rip it off. If the coating lifts with the tape then remove coating. Those are the proper methods to use to determine if the coating should be removed.