Must be glitchy on the roll-out. Doing a dummy booking DFW-PHL March 7-9 and it is only listing Main Cabin and First.
All the Main Cabin fares list as "Not Available". Only First fares for sale. No Basic Economy anywhere.
EDIT: Same thing for DFW-BWI, DFW-TPA. ...DFW-MSP, e.g. showing fares as usual. (non-Basic Econ. route)