While I can't answer that with absolut certainty, I do believe that our airline asked us to sumbit the return ticket as well prior to check-in in (and those were even booked with the same airline!), but I also wanted to point out, that the customs (immigration?) officer 3 years ago upon arrival at JFK most certainly did ask to see our return tickets, before letting us through (and he even got suspicious when he noticed that the exit point wasn't even in the same state as the entry point, so we had some explaining to do). (he got even more suspricious when he noticed som arabic writing/stamps on one the pages of my wife's passport from our trip to Dubai a few years before that ).
But yeah, for just 10.000 miles it isn't even worth the hussle to book it in such a way.