I can appreciate that. I was merely referencing how the "Rules and Regulations" prescribed the process, which, as you mentioned, was from column, but appears to form a square 6 ranks deep, which thus required 6 sub-units (2 for the "front", 2 for the "rear", and at least 2 to split in half to form each "side" - much like the British process from quarter-distance columns, it seems). I accept that once one admits 3 ranks for the walls, that a minimum of 3 sub-units would do the trick, as you describe
If I've misinterpreted the French "Rules and Regulation", I'd be grateful for a re-education. I'm also aware that alternative methodologies were introduced later in the period.