To answer Lore's question you would have to determine what sort of vegetation was growing in that region at the time the charcoal was dated to. Pollen records are a way of doing that. I believe that Kauri and Huon pine are the longest growing trees that are remotely close to that area (maybe some JWN-ers from Austrailia could verify that) and they are ~2000 years old max. btu they grow in more lush areas (NZ and Taz?) and were they even there 28k ago? I don't think so...
What was growning in the NW territory 28k years ago? It was during the buidlup to the last ice age so I'm guessing it was cold desert and scrubbrush woodland growing down there. Trees, if they were around, wouldn't be very long lived. I suspect the age of any tree they used would be smaller than the +/- error in the radiocarbon date.