I think by definition baskets are made of some type of plant fiber which is why the original statement in the article is confusing.
Amerindians fairly commonly built racks, laid the dead out, and let the buzzards remove the skin and muscle.
Frequently they'd place the bones (after suitible weathering) in ossuaries ~ large pits filled with bones.
The Mohican Indians had an ossuary near/on Shodak Island NY that dated back 7,000 years ~ maybe more. One day someone used it to build bed for the New York Central railroad. (NOTE: all of the bones have since been removed and returned to the ossuary).
Foreign immigrants to the area, if they came from the Old World, might well use different burial methods, and this could be such a site.