I took my 1986 Pearson 28-2 toe rail off today and learned how the deck/hull joint is made. If this candidate 31-2 is done the same way then I think you are unlikely to have a problem with the toe rail.
The hull and deck on my boat both have outward facing flanges. There is no wood core in the flanges, they are solid fiberglass. The deck flange is quite thin (maybe 1/4") while hull flange is at least 50% thicker.
The rub rail is placed on top of the deck, then the hull, deck, and rubrail are through bolted with 5/16" bolts on about 6" centers. The rubrail isn't sealed to the deck, but there is sealant between the hull and deck. That was pretty old and dry on my boat.
The teak toe rail is placed on top of the rub rail and bolted from below with #14 by 1-3/4" screws. The rub rail sits over the hull/deck joint bolts, so it has a concave cavity on the bottom edge to leave room for the bolts.
Finally there is a piece of plastic trim on the bottom that is held on with #10 bolts to make it all look pretty.
There was plenty of mud on my boat in the cavity under the teak toe rails (some areas of which were a little loose, that is what started my investigation in the first place). There was also damp dirt between the rub rail and the deck, especially near the beamiest part of the boat. On my boat Pearson doesn't have drainage that gets every last drop on the deck, so it's natural for water and dirt to get in between the rub rail and deck.
I think that this moisture is likely to be what pegged your surveyor's moisture meter. I don't think any of it is critical, there is no wood (except for the teak toe rail) anywhere near by to get rotten.
This does leave moisture under the stanchions as an issue. That is a concern, on my 28-2 there is wooden core there.
Here are links to a few photos:
Removing the rub rail, toe rail is already off:
Hull deck joint seperated slightly as I'm cleaning the area between them:
With fresh sealant, you can see a bulge where the area is between them:
Taking one side apart, removing old sealant, and resealing took me about 4 or 5 hours today. It'll probably take me another couple of hours to reassemble properly after making the teak pretty.