What other possibilites are there to have two attacks in the same round?
Supreme Field Commander! - Tage an average Leadership check to let members equal to presence suffer 1 Strain to take one free maneuver (not counted to the limit - on a triumph one ally may take one immediatly free action.
This is where you can attack a second time in one row.
The duration Upgrade is mostly meant for the defense-control --Upgrade to give the character the chance to defend with bonuses to more than one attack.
Other wise FFG would have named it again with Strength and wrote: "upgrade the diffculty two time for every bought rank in Strength"
To trigger something twice in the same round does not mean within the same dice-pool!