It is not Expedia. Expedia gives you a fare list like Travelocity, but when it comes to booking, it uses the standard pricing engine giving you the lowest fare for the flights you picked.

With Travelocity, you pull up the fare list, and click on the fare rule you want and Travelocity checks avaiability based on this fare rule only and prices the itinerary accordingly.
Again, works fine as long as you only use one fare code for the itinerary.

So theDeltaFlyer and Robert Leach, you might actually want to consider going to www.travelocity.com and try it out... as correctly outlined by docsbrown.