There is another instance where connection -> non-stop will not be allowed: split-fare basis. I've hit it a number of times ORD-HNL. Ticketed ORD-LAX-HNL. Wanted ORD-HNL but could not (except in IRROPS) because the tkt was actaully based on two fare basis codes - and the LAX-HNL was an el-cheapo!