I think perhaps it was an offshoot of the guilds long tradition of cutting one piece "ass backwards".
You would think such accomplished crafts people would not make such an error on a simple butt joint.
Tail end of the job and all that.
It's all so simple in hindsight.
OK, sorry, no more cracks
However, I do think Ken, that you should be praised for taking the time to study the issue in detail.