I wouldn't trust that it's OK. Can't even be sure what was meant by "winterizing". At least with my Class C all it takes is checking the manual to see which valves need to be turned and where they are located. Mine only has 2, a water heater bypass and 1 to allow antifreeze to be pumped out of the container and through the system until it runs out of all faucets, toilet, etc. Takes about $10 worth of RV anti-freeze. I would drain the system first. Only 1 spring have I had a ruined faucet and that's when a professional winterized it.