On the SMF-DEN-LAX route, make sure both segments are not the same flight number. If it's only a stop at DEN, you will likely get only 500mi (assuming you have status, 373mi as GM). In general, the allowed routing for SMF-LAX fare appears to be SMF-SFO/LAX-LAX (so really only SMF-SFO-LAX).
If a combination of two fares (i.e. SMF-DEN and DEN-LAX), then it would be valid, and many more possible routes may exist.