Instead of a particular date of manufacture, I assume that HTC merely establishes version numbers for internal quality control. In fact, if there are different manufacturing plants, I would imagine that each is issued different version numbers. Any differences within the phone hardware comes as a result of normal production changes and quality improvement as the phone production matures.
When a new version is released, the phone doesn't magically change at that point. If production changes are made, they would be implemented as phone parts are replenished. It would be silly to expect that a version number has any particular importance other than to easily pinpoint when (and perhaps where) the phone was produced.
I would think that the reason someone would want a higher version number is to increase the odds of owning a phone that was assembled with a bit more practice. From what I have seen, there has been NO difference between the parts of the various versions other than normal production variances. (For instance, a different hue to the back cover.)