I have a question, and I apologize if you already mentioned this in previous post: Isn't straight grain one of the goals for making good dowels? I believe that is something that Lie-Nielsen mentions about making dowels with their dowel plates. If I remember correctly, they advise to choose straight grain pieces for making dowels, and that the method of hammering the pieces through their dowel plates will "automatically" follow the grain, thus ending up with stronger dowels. These are then supposed to be stronger than store-bought dowels.
I cannot find the official Lie-Nielsen video, but "Worth the Effort" mentions this in his review: