If you plan on checking the polarity at RV pedestals, like I do, you get a meter with leads that will allow this. It's not rocket science.
When I get to an RV park, and the site is open, I have no idea when it was last used, or when the pedestal was last repaired. If I watched the last user pulling out, that would be different, but otherwise a new or an old park makes no difference since I would not know the day to day history of that particular pedestal. I may be somewhat over cautious, but I have not had to change any electrical parts on my RV due to a miss-wired pedestal.