Single phase is only single phase, because it's a single phase in relation to neutral, which in itself is normally tied to earth.
If you don't relate neutral to earth, then you essentially have two phases, and if you add a centre tap transformer between those two 'phases', the centre point essentially gives you a new neutral, although it is actually a 120V AC output in relation to the original neutral, however in relation to the two phases, it's a neutral.
The key thing to understand is in voltage terms, everything is relative.
Think about how a typical 110VAC supply works, with it's centre tapped neutral being seen as 0V, and supply two 55VAC phases which are then used to form 110VAC.
The only reason Transwave and the like use a transformer, is to increase the single phase from 240V to 380/415V. Beyond that, they're using capacitors to create the 'false' phase. If you don't want typical 415V three phase, and your machinery can run on 240V three phase, there is no need for a transformer.
If you don't relate neutral to earth, then you essentially have two phases, and if you add a centre tap transformer between those two 'phases', the centre point essentially gives you a new neutral, although it is actually a 120V AC output in relation to the original neutral, however in relation to the two phases, it's a neutral.
The key thing to understand is in voltage terms, everything is relative.
Think about how a typical 110VAC supply works, with it's centre tapped neutral being seen as 0V, and supply two 55VAC phases which are then used to form 110VAC.
The only reason Transwave and the like use a transformer, is to increase the single phase from 240V to 380/415V. Beyond that, they're using capacitors to create the 'false' phase. If you don't want typical 415V three phase, and your machinery can run on 240V three phase, there is no need for a transformer.