What did he define as wet?
What meter was he using and what was the reading on it?
Was it a GRP-33 meter with readings over 30%?
Did he sound it out?
How far in each direction?
It takes lots of time to saturate more than a few feet from a stanchion so that means that it could have been saturated & leaking for a very long time.
Personally I have no huge problem with a deck with "elevated", or what's considered "low moist" in moisture meter language, near critical areas as long as it sound out and is not still leaking.
If he was using the fairly standard GRP-33, as many surveyors do, you need to remember that rot
starts setting in at about a 20% reading on that meter but it still may take years before any structural failings have occurred. If he is getting dull thuds near the stanchions walk away as the core has turned to mush or delaminated..
This is considered saturated and this deck sounded like you were tapping on pudding:
Although this is technically considered in the high "moist" range, and not in the "wet" range, this deck still had some delamination and dead thuds around the chain plate. As I mentioned above when using the GRP-33 or it's sister meter the CT-33 rot begins to set in at about a 20% reading on these meters..
Just for reference this is considered bone dry:
P.S. Professional core repair usually begins at about $500.00 per square foot and goes up to about $1200.00 per square foot depending on your level of cosmetic requirements for the repair. If you want it to look like it was never repaired it will cost closer to $1200.00 per sq foot than $500.00