I got a hunch there are some logs on shore already, maybe only a few, but I think one of each variety, possible more for comparisons sake.

The why:
Looking back to when they put out pictures. They have hydraulic chainsaws in those boats. You can tag and identify a tree type from the surface, but if you want to check the condition and quality (which they did say they identified and determined quality in a previous statement), make sure it's not water logged you got to do some cutting below the surface. I would imagine they were able to bring some ashore to verify quality. You can see what's inside the log unless you cut it open. Maybe just wishful thinking, but I tried to come at it with what we have seen.