The reason why the baguette needs a knife is that the dough will expand rapidly in the high-temperature oven at the early stage of entering the furnace, and the surface of the baguette is often knocked tightly during molding. At this time, the dough inside will not rise, but will break through the surface at unexpected weak points, resulting in ugly "cracks" or "big bubbles"
This requires us to manually cut the knife and guide the expansion force to these cuts, so that the shape of the finished product can be effectively controlled. Therefore, the standard of successful cutting is to see whether the incision is completely unfolded.
To sum up, the depth of the blade of baguette depends on the expansion potential of dough in the oven.
If the dough is very stiff, it will only ferment for 6 or 7 minutes at last, and the oven temperature is high enough, it can be cut deep, because the dough will expand a lot and quickly in the oven, and it can be completely expanded before the deep skin is cut, baked and solidified.
However, if the dough is low in gluten (there are a lot of rye and other raw materials), or if the oven temperature is not high enough after fermentation, then it should be lightly cut or even not cut, otherwise the dough will not expand during baking, or the expansion will be little or slow, and the cut marks on the skin will be baked hard before expansion.
If the final fermentation really reaches 10, or even more, then the dough will collapse to you.