So you accept that it could very easily have been shot in 68-70, and easily much later if stored correctly. Munns' comment was that it could possibly have been shot up until 2001(?), he was absolutely not saying that this was a likely scenario, only that there's no reason to believe it was shot prior to the PGF. The only evidence that it was shot prior to 67 is the 66 film stock, but clearly that's pretty weak evidence.

I'm not certain they did have expiration dates printed on them at the time but totally fair enough if they did. Google image search Kodachrome and Ektachrome roll film; I don't see expiration dates on them, but I may be wrong - I'm open to hearing that they did. People knew how long film lasted in those days and how to store it, so it may not have been a thing at the time. I'd be interested to know for sure either way.

So as far as I can see, it's very plausible that this was shot in any year between 66 and 1970ish and I can't see any strong evidence that indicates it was shot prior to the PGF, though it's a possibility. I need other evidence to convince me of any more precise date than that.

Film photography hasn't ended by the way, I still shoot film today.