Baguettes are supposed to be made with high-protein wheat / bread flour. Proper Southern Biscuits are supposed to be made with low-protein flour.

I'm somewhat surprised: in my grocery store, there are "cake flour", "bread flour", and "all purpose flour" in the flour section. It only took a brief search to learn the difference (and which had higher or lower protein counts).

Further research (actually book: "On Cooking"), describes the uses of each flour. In effect: high-protein causes gluten formation, which is necessary for a proper "doughy" bread like Baguette, but is counter-productive for southern-style biscuits.

Possibly, but people are pretty aware of the flour difference. Even back in the 60s Julia Child mentioned it in her cookbook (Relevant TV episode: https://youtu.be/9iH3hjDUhWw)

I suspect the real difference is in the customers. I've heard people arguing over which bagels or donuts are superior, but I've never heard such a conversation for baguettes.

I've run into the opposite problem. Most grocery store baguettes I've found have been too soft, almost like hot dog buns.

I suspect that's mostly due to par baking, since a lot, arguably most, of the grocery store baguettes are pre-made, par baked, and shipped frozen. They're then baked again in the store, which often leaves them soft and chewy or rock hard, depending on how they're baked a 2nd time around.

Lots of dough conditioners are also common, which helps make them soft. Often too soft, in fact, so they overcook them.