Sounds like salesman was telling you to use generator while traveling down the road to keep residential fridge running if you are plugging your 30 amp cord into onboard receptacle.
Generally, our experience is if our fridge is at proper operating temps and contents within are cold we can go a few hours without any cooling and just plug in when we arrive to our site.
The majority of RVs have absorption type fridges where they can utilize propane to cool while underway to their next destination, of course on propane mode they should be turned off while refueling.
