I don't have any similar stories or anything different to add about the effects of cumulative bad decisions.
At least they were wearing PFDs.
I'll say this about foam flotation. I think you'll find that the flotation rating of foam is predicated on that foam being DRY. If the foam is water logged, as so many find in their boats, the flotation rating is useless. If the foam is waterlogged (before the boat sinking), then the "hidden" weight of that water counts against the weight rating of the boat.