Rhosyfelin -- the date near the crack

With respect to the theory that a rhyolite orthostat was taken from a "recess" near the tip of the Rhosyfelin spur, I have been looking again in wonderment at the following extract from Parker Pearson et al, 2015:

"The most probable dates associated with the removal of the rhyolite pillar from its recess are c 4590 BP and c 4667 BP, provided by carbonised hazelnut shells from the small occupation layer just 1.5m away from it."

This is pretty extraordinary. 

Here's a story. Somebody visits Stonehenge and looks at it from a hundred metres away.  He wonders when it was built.  He asks a passer-by how old the monument is.  The passer-by picks up a discarded newspaper from the road, which has yesterday's date on it.  "Of course!" says the visitor.  "That shows that it was built just yesterday!  Isn't that amazing?"

Another story.  Somebody looks in wonderment at a cave in the cliffs on Newport Sands.  He wonders how old it might be,  and then notices an old can of cooking oil among the flotsam and jetsam on the beach nearby.  Purely by chance, it has the date 2003 printed on the side of it.  On that basis, he decides that the cave was formed in the year 2003 by the same fellow that used the cooking oil.

Illogical?  Yes indeed.  Enough said.

The paper:  Mike Parker Pearson, Richard Bevins, Rob Ixer, Joshua Pollard, Colin Richards, Kate Welham, Ben Chan, Kevan Edinborough, Derek Hamilton, Richard Macphail, Duncan Schlee, Jean-Luc Schwenninger, Ellen Simmons and Martin Smith (2015). Craig Rhos-y-felin: a Welsh bluestone megalith quarry for Stonehenge.   Antiquity, 89 (348) (Dec 2015), pp 1331-1352.
http://www.ucl.ac.uk/news/news-articles/1215/071215-stonehenge-bluestone-quarries