This happens to me all the time when using the Award Calendar. The calendar shows SkySaver availability, but selecting those days and clicking "Continue" lists nothing but SkyChoice.

Selecting "Search by Schedule" at this point usually shows a LOT more routings, including the SkySavers available on that date. Not sure why they don't appear in the initial list - perhaps the system selects the best routings for that day, which are usually SkyChoice. (?)