Typically any car produced after July of a given year is branded as the following model year. Look at the VINs on 2009s. Here's a sample:
JM1BK34M791246407.
The 10th character in a VIN designates the official, NHTSA, manufacture-specified, model year. A represented 1980, B is 1981, and so on and so forth (barring the exceptions of I, O, Q, and U which were never used) until Z = 1999. Starting in 2000, a number was used. So, 0 = 2000, 1 = 2001.
Notice the "9" in the VIN above? Copied from a MS3 that is labelled "2009" on the Window sticker. So you're telling me that in addition to going around swapping on "2009" window stickers, dealers went and changed the VINs too, in violation of federal law? Riiiiiight.
The argument that "09s are just relabelled leftover '08.5s" is no more valid than saying that '08s are just leftover '07s. If anything, is is the "08.5" that doesn't really exist.
Not to mention the afformentioned ECU issue.