No dog in this fight and likely won't be traveling through AZ anytime soon and my MH is not diesel...but, out of curiosity, I did some searching for GA and some other states laws on this and all seem to be related to the IFTA (International Fuel Tax Agreement) between the 48 contiguous US states and Canadian provinces. The
IFTA Exemptions website shows AZ and a few other states that do not exempt RVs. GA is listed as exempting them and the GA code I found listed RVs (for non-business use) as being exempt.
Ironically, IFTA headquarters is in AZ!