I've seen a couple similar incidents when muskrats moved into the muffler
system of power boats at dock
and then chewed thru the muffle hose.
We are talking 4-6" diameter inlets so crash pumps aren't likely to solve a major break.
Most likely, this is a first shot by the insurance
company. If you accept it, they pay nothing. If you challenge, they ma back off or meet in the middle. If you can demonstrate a maintenance
schedule even if just observation, you will likely have a much stronger case.