Bread doughs develop plenty of gluten if properly kneaded and in appropriate flour to water ratios. Missing the additional water from a dry(er) butter will do little to no damage whatsoever. While the additional butterfat will coat some of the flour molecules and prevent them from stringing together, the difference will be modest at most. Moisture levels in the air and the flour will affect the final product much more than water content in the butter which is why it is always a bit of a guessing game, even if baking by weight from a recipe. In yeast doughs rich in butter the benefit of using a better butter would be better flavor.
Plus, one always has the option of adding additional water to make up the 2-8% loss (by weight of the beurre sec), if one is so inclined. Personally, I’d follow the recipe to spec. and add extra flour (or water) if the dough looked like it required it.