Sometimes your fare will be actually pricing as 2 roundtrips if you are connecting, if that "prices" cheaper than the regular RT tariff. This is completely legal, if the airline autoprices it and the whole itin is on 1 tix. Having some familiarity with pricing, there is no rhyme or reason for a lot of it. Well, actually there is, but its not apparent to the public.

In fact, some of the quirks are signals from airlines to each other to see if fares are going to go up or down. This violation of antitrust has never been proven in court.