We're getting a little tangential here, talking and hinging so much of this theorizing on second cutting. But perhaps, this is just part of my personal biases against second cutting, I see it as unnecessary, inefficient, and inferior technique. And such opinion should not enter attempts to understand historical technique.
All the same I think the 23” tangent might be the wrong road...
To answer Tim's questions – You don't want the two foot in the area of joinery, or a row of it, because you don't want to take the chance of cutting it or part of it away, it is simply too important. It is occasionally placed at points other than two feet, always to avoid joinery. I remember the thread and its photo and the brace you pointed out, I'm guessing it may have been a recycled post and the mark and it's proximity to that brace may have been happenstance
As I engage in scribe work, it often enters your thinking that this or that circumstance may have influenced why little techniques that were and continue to be common practice came to be so.
I believe Two Foots ( which predate common use of squares by hundreds of years ) are where they are, because it is an area (below the plate and above the braces) where other pieces where seldom joined, allowing for consistent placement of this so important mark.
Could the placement of the girts in this particular barn have been this simple ? How big is the over hang ? Where is the soffit and its bed mould ? Was its seemingly low placement about nailbase for the trim ?
"We build too many walls and not enough bridges" - Isaac Newton
