I to uderstood that in square rule the blade of the square was used for layout from the outer referense face. In scribe fit this face would have been hewn to a tighter tolerance probably using a square ir similar instrument.In heavy duty frames 4x4 braces where sometimes doubled up to on tying beams. I also concur that the brace on the out simplyfies and strengthens the joint considerably. If the brace was in the middle of a 10x10 for instance then the craftsman (or apren.) would have to bore a peg hole fully through beam.