Oh, I realize I'm likely in the minority here. Not trying to convince anyone otherwise. There is something though that intuitively does not make sense to me to be eating or feeding acidic food ALL the time. It's not about the flavor of sour for the birds, but having SO much acid in their tract, all the time. I'm with you on going for good gut flora, but I'm not convinced that more is better in this case. And my "gut feeling" about it all could be just plain wrong. Soaked/sprouted I can understand, but highly acidic I don't. Perhaps I will change my tune one day, I've been known to do so a time or two before!
Mine are cooped at night and completely free ranged during the day {no run}. I feel like they are definitely getting enough other stuff {snakes, frogs, mice, moles, voles, berries, grass, etc} that their gut isn't completely acidic. I am not sure there are any hard and fast "rules" less keeping them healthy.