
It wouldn’t surprise me if theyre all related. Natural transitioning isn’t random, it’s based on genetics deactivating one gonad and activating the other. The trans chickens are likely infertile due to the genetic expression, but their parents likely had the genetics without being expressed.
It’s rare bcos both parents have to have the unexpressed genetics and farms generally either let the chickens do whatever they want (aka the random chance decreases) or selectively breed away from it because they don’t want infertile chickens (aka there’s no random chance). I’d venture to guess that your bf had something closer to family/pet chickens than a large commercial farm