I don't agree with that tech support person. That would discard the system's current flexibility--and one that Ancestry.com already employs repeatedly. Consider their state census collections. In all that I've seen, there is only one source for them, regardless of date. (I always have to remake them.) The date is distinguished in the citation detail.
The solution is not to force users to create a new source for each edition. All that matters is how the source citation is formatted whenever it's used (e.g., in a report). How we get there doesn't matter--as long as the methods available do not prescribe countless hours of data entry.
Additionally, it's hardly a defense for them to say that the field in question here serves no purpose. That's a bit aggravating.