... But I didn't 'think' very hard on this one. (You certainly did!) I kinda throught the question was a simple one so I kinda answered it that way.
Yes, just because it's a conductor of electricity doesn't mean it's going to conduct electricity. Take that along with the siding's TENDENCY to conduct electricity and, well ..., I guess one could weigh the 'odds' of it happening.
This site actually states that the 'grounding provision' was removed from the Code. Medina-Gazette
I don't think the Inspector is far off but maybe its required by local Code. I donno.
Sorry, Henry, that you 'thought' so hard on this one. It sounds like you were leaning more towards 'talking' about the 'merits' of grounding the siding vs. why aluminum is grounded in and of itself (or why it is or isn't a conductor of electricity.) I'm not going to go near the why or why not it should be done. I'll leave that to the Homeowner ...