Only LTS releases will get point releases, but they're not really "releases" just refreshes of the ISOs, it's nothing meaningful as far as installed systems are concerned (I guess it's useful for setting milestone goals or something, but that's not technical). They take the updated packages, throw them on the CD so you don't have to download as many updates after you install.
Having an installed system that you updated completely the day the images were released* would leave you with the same system.
And while we're being thorough they're offset by three months, so January an August.
See http://www.markshuttleworth.com/archives/146 for more information (including fancy pictures).
* It's likely a day or two before release, whenever the images are created, yadda yadda.
It's a naive, domestic operating system without any breeding, but I think you'll be amused by its presumption.