On the web site for SIN-IAH and IAH-SIN (9Nov /19 Nov), it shows the MAN stop both ways but still includes the Moscow route as well for the return. But it doesn't come up with anything for MAN-IAH-MAN as Viscount702 says.
I assume the web site is still being updated, but it was stated elsewhere that the new flights were now bookable which I took to mean MAN-IAH. Whether or not that is correct, the M.E.N article and Ken O'Tooles's comments certainly affirm that MAN-IAH is a new route.