You are mis-reading the info.
It is amongst a very few (2, to be exact) vintage woofers with positive cone motion.
+1, er, +1.5!!
Perfect! That is the way JBL designed and built them. You are good to go!
btw, 1 MILLION points to "Eaulive" for doing extensive searches before posting! He resurrected a 2003 thread. Yeah - the system is cumbersome but it is working!