I guess it's better late than never...
I finally got around to getting this from our Plumbing Inspector, who got this at a recent seminar.
From the IFGC (International Fuel Gas Code, 2009)
310.1.1 CSST.
CSST gas piping systems shall be bonded to the electrical service grounding electrode system at the point where the gas service enters the building. The bonding jumper shall not be smaller than 6AWG copper wire or equivalent.
That is probably where the inspector in the OP obtained the #6 size from.
Jurisdiction here (NJ) is the Electrical Inspector, and a NJ Lic EC is required to do the install and obtain the permit for same.
