I think everyone has their own interpretation of what "de-winterizing" really includes. For some, it's the "whole ball of wax" with system checks, appliance checks, battery checks, leak checks (plumbing, gas and coach), bearing/brake service, washing/cleaning and filling the propane, etc. To others, it's flushing the water lines, filling the fresh water tank and adding Clorox.
As an example, this link is to the Camping World services explanations. You can see their "services explained":
http://www.campingworldofnewhampshire.com/service
As listed, "De-Winterization After the long, cold winter, make sure your system is clean of antifreeze and checked for leaks."
So, it seems that for CW, "de-winterization" means flushing the water system and checking for leaks. Also listed are a host of "other services" such as "45 point inspection", "furnace inspection", "refrigerator service", "air conditioner service", etc. There's even a separate "water system service" that's "Recommended annually to prevent water system failures."
So, in my way of thinking, if you didn't get an explanation of "what's included" in the de-winterization you requested, it's pretty much open for interpretation as to what the service actually included.
Also, consider that at many RV service centers, a "front to back" service request (what some people do every year to de-winterize their RV) would probably cost upwards of $1,000 or even more.
I'd say that if you're not satisfied with what was done, talk to whoever did it and ask what was included. There's probably a significant difference in what you "thought you'd get" and what they "include for that price"......