Cored hulls by good manufacturers like HR last as long as solid hulls. The core
nightmares are in boats from lousy builders. I'm sure that HR installed all underwater fittings in areas with no core
Of course, there is a risk that someone installed a new underwater fitting without cutting out the surrounding core. But owners with enough money
to buy an HR use boatyards
that are expensive enough not to do that. And while Divycell isn't as water
resistant as maybe Corecell - it's a lot better than balsa.
If the foam is full of water, the surveyor will know immediately. If there are a few bad spots, it's cheap
to fix. But most likely, it's fine.