Don't take this as gospel, but I discovered with my bandsaw, which was marked 28-280 on the boxes it came in, that it is really a 28-203 (I think) with a 1 HP motor and enclosed base. That's what makes it a '280.
There are other iterations as well. 3/4 HP, open base, etc., which, as you and I are both hinting at, can cause a change in the numbers.
As far as the Platinum Edition is concerned, that was around for only a year or two, and to my knowledge, didn't have any effect on the model numbers--just paint color. The X-5 series seems to have thrown numbering all over the place. I couldn't depend on any model number nowadays as having relevance to those I was at one time sort of comfortable with.
Unisaws are the worst, I think.
Frank Broecchter (sp? Sorry, Frank) may be able to answer some of your questions more authoritatively.