GS > May I ask a simple question? Are the words Arab and Islamic been considered throughout this discussion and in the books mentioned as synonymous? 

Most certainly not by myself, and surely not others.  I have not read Kuru, so am not sure how hard the lines are that he draws regarding ethnic and cultural generalizations.  It is true that (say) Maqrizi claimed Arab descent, and his criticisms were primarily aimed at his 15th century Mamluq overlords, who were overwhelmingly non-Arab.

The general case seems to be that copper and silver usage and declined, as did concern for scholarship, alongside the rise the new largely Turkish military elite around 1000.  That is broadly correct from what I have read. 

However there are very important exceptions.  Afghanistan under the (Turkish) Ghaznavids quite deliberately rejected feudalisation and maintained a huge silver coinage into the 11th century and beyond.  And fostered such great intellects as Al-Biruni.  I see the roots of that situation in the particular stance of an individual, Sabuktegin.  A matter we would miss if wearing ethnic or cultural spectacles.

Rob Tye