I would say yes he did. Those aren't huge numbers for a guys his size at his peak.
With respect, I'm not sure I can agree. Franco did have decent arms, but he was, what, 5'4"? Mentzer was known for his awesome arm development and, while standing a fair bit taller, said he "only" had a bit over 18.5" arms in contest shape.
I know some of the 212 guys around or shorter than Franco probably have 20" arms, but they are in some cases 20 lbs. heavier and no strangers to site injections out the wazoo

Nonetheless, you are a competitive bodybuilder; I am currently not and haven't been for about 18 years. I will defer to your judgment.