But how otherwise would you describe chopping a mortice given the use of a bisaiguë? Certainly not by pushing it into the wood, a very difficult action with a straight cutting edge. Even the translation out of the French you provide says that the sheer weight of the bisaiguë replaces the need of a mallet, implying some use of that weight, I presume through some kind of percussive action. The auger or pre-boring would provide a solution to the guidance but also implies that without this step first the bisaiguë is only a half useful tool on its own.

I came across what I found an incredible statement by what is otherwise a reputable Flemish institution on carpentry and tools, and which I almost hesitate to repeat because you know how these things take on their own life, but it said the hollow handle would be filled with hot coals in the winter and stopped with clay to keep the hands warm. I doubt this. A lot of French carpenters are using all metal chisels or one piece chisels. I don't like the practice either.

I think the working height and why it varies from place to place could be a difficult thing to clarify but with the French it begins even before layout at the point of preparing the timbers where they score from on top and edge down low.