Where is pointer, where is pointer?

Yeah, I know you've probably moved on from royal-wedding-land, but I didn't watch it, so I'm catching up slowly, via print. Anyway, I was checking the text of the vows the other day when I ran across this very odd report:

Prince William then slipped the ring on the bride's index finger.*

Not very traditional, and also not true, judging by this AP photo:

I don't know anything about the source, International Business Times, except what I see on the website, but it doesn't seem to have any obvious problems with standard English. But I don't think I've ever seen "index finger" substituted for "ring finger" before. Anyone else?

* I hope you weren't expecting me to complain about "on" for "onto."