When all else is said and done you are a only guest on some ones property. If having a tagged lead is part of the conditions of entry stated by the park management then so be it. If you don't like it move on to the next park. Problem is why stop at the power lead. The van and everything in it should be tagged. Watch the $$$ build up. How many out there have had their vans checked since purchase, not many. When you rock up to the entrance of a park is the person booking you in gonna come out and search your car and van for tags, I don't think so. If you have tagged all your electrical stuff do they know who did the tagging, I don't think so. If you strike a park wanting any of this just ask to see their records of testing to see if they are up to date, probably find they aren't. I'd be wary of any park person tagging leads, who knows if their competent. No one has the right to cut the plugs off leads that do not belong to them. Becomes willfull damage to private property. If a tag is filled in and placed on an item it could become a legal document which opens up another can of worms. Like others have said, is it a grab for cash by some, arse covering for others or just more bulls**t by the caravan parks association.
Just a side note and that is both my daughters attend Calisthenics competitions at venues and most of them require anything 240v to be tagged.
End of rant.