Hi Mark and all--good discussion and input
that is very interesting Mark, but there you go, no one should say only one way to do everything, right!
Many of the barns that I have inspected had bottom mud sills 12" square.
(this is just a comparison)
So if you used a mortise and tenon attachment at the corners, the strength of the corner would have to rely on the strength of a 2 by 11 tenon, or 22square inches of wood.
if you used a half lap the strength of the corner would rely on a 6 by 11 or 66 square inches of wood or 3 times as much holding power.
This is just my observation, I am sure that the corners were done in both methods, I have never noticed or seen the mortise and tenon used at the corners, but then there is alot of things that I haven't seen, it is nice to hear that you have seen this method used and share it here with everyone.
NH