I didn't read all the posts, but my opinion, is that when you see baby chewing and grinding foods against their gums, and baby can pick the little bits up and put them in her own mouth and chew and swallow, that baby's ready for finger foods.
With my little Fred, that was at 5.5 mos. He stole a cracker off my plate, proceeded to bite off a hunk, chew it up, and swallow and then bite off some more. With George, I'm guessing it was a little after 6 mos. With my little niece, she hadn't really mastered that until now, and she's a little over 8 mos. old.
I don't think teeth matter much, until the molars come in, because they're good for tearing things b4 that, but not so much with grinding. My boys had no teeth at all until 10 mos and 9.5 mos respectively, and they both were eating finger foods well before that. Plus, there are teeth underneath the gums, so chewing with their gums is not the same thing as a really old person without teeth gumming their food. It's solid under a baby's gums, iykwim.