I think the dealer is blowing smoke.
But in order to retain the ten year roof warranty you do have to check the roof radius sealant - every six months . Winnebago uses a special adhesive sealant. They have changed the brand a few times and you might want to call customer service to get the brand for your coach. You can also go online to their web site and get a sealant call out sheet.
You push on the fiberglass next to the sealant and see if it moves away (very small crack) from the gutter or fiberglass.
To repair it customer service said to use a flexible knife blade to carefully remove the old sealant and then re-caulk.
They used Manus-Bond 75-AM from Manus Products Waconia MN. 952 442 3323 on my motor home.
Below is a cross section of the roof construction.
I have needed to re-caulk the satellite dish cable entry point on the roof once. Dicor self leveling sealant is what is used in the areas other than the roof radius.