I'm looking into flying from SFO to OTH (Southwest Oregon/North Bend, OR) in October, and it looks like it is cheaper to fly SFO-LAX then LAX-SFO-OTH (and vice versa) instead of directly from SFO to OTH, because United publishes S class fares for both SFO-LAX and LAX-OTH, but not SFO-OTH (cheapest fare seems to be V class).

Is this really true? Obviously the longer routing earns me more miles, but how can United do this? If I book this, is there any chance I can fly the more direct route? (Maybe on the way back?) If I check luggage, will it actually travel with me through LAX? On the way back can I short check it to SFO, or if I don't travel to LAX, will my bags eventually make it back to SFO? Anyone done something crazy like this?

Thanks!