I agree with both comments. According to the Customer Service rep and the ticketing agent, if no designated Early Returns seats are available the website drops you back to the member log-in page, requiring re-entering ID #, password, departure city and date, destination city and date. Which takes minutes. Then it happens again with your modified query.
Even their ticket agents do the same thing if you are willing to pony up the $25 booking assistance fee.
The ticketing agent was unable to tell me when or where I could use my Early Returns miles, and gave up after trying 10 different options. It turns out that if you try to book several months out, it is no better because they have not released any seats for the frequent flier program until they have analyzed they won't be able to sell them.
So it would a genuine stroke of luck and would take a lot of effort to get a seat any where with their Early Returns program.
It would seem that this program and their websites are designed to deny use of benefits. It is fraudulent.