I guess there is no possibly of those pieces got out there on an ice float the broke or melted... And there was no distinct rock line up they mention. I think it’s just a fluke. They clearly just grabbed the top layer of sentiment. I would think 10k years they would be a touch deeper...
Sediment*
There’s no possibility that a couple of stone tools wound up on the same piece of now-submerged land where human-built structures were found? Yes, that’s pretty much what they’re saying.