Well, uh,...excuse me but whom among you have actually measured the volume of your board(s)? If you haven't ever done that, then you don't have the objective data to mount the opinions put forth here.
I think Starboard has said in various places that the board numbers are changed from year to year to distinguish models and/or minor tweaks in shape. While I don't recall explicit statements that the board number doesn't match the stated volume (e.g., the Kombats have had a propensity to have the last digit be the year of manufacture), it is implied.
There is some merit to the notion that if a spec is given it should be the spec, that makes sense in the same way that it is logical to make sure that a clock is telling the correct time. However, in most applications people don't really need the exact time down to the second, though in many applications that is necessary. So it is with sailboards.
If you really
need to know the volume of your board, i.e., the floatation, then you ought to have your own tank for testing it frequently...lest all your board dings let in too much water.