Just because I had some time, I called the broker who listed this boat. It's a donation, and even though the hull had substantial plating replaced there is currently an issue with the bilge where...wait for it...the current owner poured something to add weight to the boat to reduce the rolling because...can you imagine...the boat was "a bit top-heavy".
The broker does not have the $.5mm receipts in hand but has talked to the yard where the majority of the work was performed and believes that it was indeed spent.
I wasn't able to get a solid story on exactly why the hull was substantially re-plated, except that it might have been because the plate that was originally used was under-sized. I had originally read the ad to mean that the re-plating might have been done for any number of reasons other than rust (easier to remove the engine, replacing / enlarging tanks, changing the hull form) but now I truly have no idea why it was done.
Also, did anyone else notice that the price dropped THIS MORNING from $103K(ish) to $95K? Not related to this discussion, just because "it was time for a price drop".