Rex Dart
[12] Conqueror
It's because it was an arcade port, and characters only had one weapon in the arcade version of SC2.In SoulCalibur II, though, there was no excuse for Inferno not being able to use Soul Edge all the time, but he still didn't.
I think Inferno used Soul Edge variations at the end of Weapon Master Mode, but always the same three. I can't remember what they did for Extra Arcade.