Yeah, I was confused by Windows' apparently-large share as well, and I figured it was a definition thing as well, but if you look at these sales figures:
Microsoft sold 14 million smartphones (or rather, their device partners, probably mostly HTC back then) in 2007, but according to this article from 2007, RIM was running at about 9.6 million devices a year, which matches what wikipedia says:
I suspect fleet deployments were a big part of their sales.