I am confused about this, now. I have several domestic Basic Economy tickets purchased and all of the emails have the same standard language about baggage fees. They all state that I have to pay $30 a bag, even though I am pretty confident that I don't because of credit card benefits.
I can't find the data from older flights that were all Main Economy or Award flights, but if IRC they also had the same baggage fees listed. And, I still received the free bag for me and companions for years using the Citibank Platinum MC.