Plextor 712A does not read DVD DL?

vbimport

#1

“Since the Plextor 712A does not read DVD DL …”
This is from http://www.anandtech.com/storage/showdoc.html?i=2086&p=3 ( at the bottom ).

What is the purpose of DL DVD+R9 if not even the newest DVD burners can read it ? I thought almost all DVD units can read DL.

Am I misunderstanding something ?

Regards,
xerces8