I agree about the level of DOTD competence displayed with regard to routing. Bertrand/College should be swapped for Ambassador Caffery north of Johnston Street. That would place all of Caffery under state control and create a logical Lafayette half-bypass.
There is a logic in that Bertrand Drive is already a state route and Ambassador Caffery is not a state route between Bertrand Drive and Johnston St. So the US 167 reroute follows road that's already under the state's purview and doesn't add any mileage to the state's plate.
It's lazy logic, the sort of minimalist quality that we tend to get in Louisiana. Only DOTD sees any sense in Ambassador Caffery not carrying LA 3073 all the way to LA 3814.
You seem to see this as transportation. It is just the way LADOTD and the local communities negotiate and trade highway maintenance / construction back and forth. Sometimes they will exchange lane miles from a newly refurbished stretch to one that is barely open almost as soon as DOTD has finished the upgrade. This is primarily done when DOTD has extra money, but that is not the only time they do it.
Why
wouldn't I see this as transportation? If there's no navigational aspect to it, then it doesn't need to be signed. There's no compelling reason for the BGS for Evangeline Thruway to have "LA 182" on it unless LA 182 has navigational value. "Evangeline Thruway" should actually be on the sign because the name "Evangeline Thruway" has navigational value. LA 182 doesn't have any navigational value within the city of Lafayette.
I think this is a fair criticism of DOTD. I've lived in Tangipahoa Parish for almost 10 years. You could put a gun to my head and force me to tell you the street names of US 190, US 51 and US 51 BUS. And I expect I would fail that test. Because none of the interstate interchanges with these roads have the street names on the BGSes. Just "Hammond." I'm old enough to remember when the LA 182 exit from I-10 read "Lafayette / Carencro" instead of "N University Avenue."