Boris has eaten quite a lot of greenies and has always been fine. And he did eat them fast, pretty much in 10 minutes too. So I don't think you should worry too much, but it shows what a responsable owner you are
Oh and I stopped giving them to him after I read the dangers too, even if it's rare I'd rather not take the risk. But honestly my dogs eat a lot of crap, and I always worry a lot but when I see what passes through sometimes I realize I probably worry for nothing, but it's important to check that they are behaving normally when you have a doubt.
Ironically, Tips is the one that got a problem once, from swallowing the knot of a rope toy. He puked it, but he still seemed sick afterwards and it cost me $400 in vet bills just to make sure there was no blockage. I can't say I was pleased, so now they have no toys except the really hard ones, nylabones and sterilized bones... And I found the rest of the rope toy while I was cleaning poops outside...