Correct. Motor design is a compromise. Wound rotors are concerned with extreme peak torque but since starting torque and pull in torque are simply not issues we don’t need to push that. The shorted torque curve is roughly NEMA design C. Core losses are fairly high:
As far as efficiency though they are not particularly inefficient. Above 200 HP everythjng is 99%+ efficient: Improving from day 99.6 to 99.7% doesn’t make a difference. I do see a few very old 150-250 HP wound rotors but these are pretty rare.