Travelocity fare rule summaries show (unless you're seeing something I'm not) co-terminal info, but not valid routing. Those are cats of two different stripes.

For example, PDX-HOU use to allow this really convoluted routing through SEA-SFO-LAX-PHX-DEN-etc. The base fare was the same as if you flew with one connection but you'd pay a nominal fee for the extra segments - well worth if you're doing a miles run.