In the past, I have exported pier loads from ETABS to a program like S-Concrete or SPColumn to design. L-shapes can be formed in the section designer in ETABS but the drawing procedure is definitely a nightmare if you have an irregular rebar layout. I am simultaneously surprised and not surprised that ETABS is giving you some weird capacities, though I would note to be cautious that your 2-D section's axes match up with your 3-D model wall axes if the legs of the L are not the same difference, since this will definitely affect the capacity calc.

I recall checking a P-M curve between SPColumn and ETABS for a T or L-shaped wall a while back and they came out pretty close to one another, but I'm not 100% certain.