I actually kind of agree with you, except I think that all Slim revisions and the like should be separated as well (WII IS TEH BEST EVAR!!!!!!!111!!!).
Honestly, though, there's no real point in separating the bases -- what matters is that there is a 145m base to buy DS games with. You could argue that rebuys contaminate the numbers, but PS2 owns DS in that sector.
“These are my principles; if you don’t like them, I have others.” – Groucho Marx