Yes, the optimum "load" impedance for highest output power compression is generally not a conjugate match.
Steve Cripps has a IEEE MTTS conference paper that does a nice job of explaining matching a transistor output for maximum saturated output power.
Cripps, S.C., "A Theory for the Prediction of GaAs FET Load-Pull Power Contours," Microwave Symposium Digest, 1983 IEEE MTT-S International , vol., no., pp.221,223, May 31 1983-June 3 1983
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1130864&isnumber=250...