2.7x seems steep, but...
I don't think hurricanes are the big factor. Most boats sink in the slip -- and I don't think from hurricanes.
The older the boat the more questionable maintance history it has accumulated, the more "owner engineering" happens, the more forgotten things age, and the greater likelihood of a hidden problem. Surveyors are, well, of variable quality and objectivity, and even the best are very limited in what is accessible.
And, possibly, as you suggest, there may be a statistical measure that shows directly or indirectly, in isolation or incorporated into a bucket, for right or for wrong, that owners take care of newer boats better than older ones, even if they own both.
All I can suggest is shopping around for coverage.