I've read that "let them dry on the plant" advice in many places too, but in my climate that actually gives markedly worse results than picking them a bit early. So for my dry seed I pick them while the pods have been all yellow for a while but well before the pod turns fully brown & crispy (in the shelly stage or a bit later), and either shell them right away or leave them drying indoors in the pod for a couple days.

Beans that are old enough to show the pattern well dry up nice and without wrinkles and germinate well in subsequent years. Ones that are still green get shriveled and aren't so great for planting. But the green ones in your photo look pretty filled-out and well on their way to full maturity, so I think that after drying they'll be wrinkly but not lose too much body. I've tried drying some very young green ones, but when cooked up they taste ok but are pretty much just skin so the texture's all weird.

As long as they dry out before dry storing them it's fine. If your in it for saving seed for replanting, then test the germination rates after they dried. (Just throw a few in a cup of water)

Those that have a distinct pattern in the shelly stage & are then dried, should be OK for planting... at least for next year They might not remain viable for as long as those which were allowed to fully mature, so I concur with the recommendation to do a germination test before planting.

I last grew those beans 10 years ago & liked them, don't know why I never grew them again. It would be interesting to see if they are still alive.