This is my recollection of the Leyton connection:
It is clear that current from X1 to X0 is reflected as current on the H1 to H3 coil.
It is also clear that the current from X2 to X0 flows on both of the low voltage coils, and that the current must be exactly the same in each coil. Thus the current in the H1 to H2 coil must be the same as the H2 to H3 coil (neglecting the slight magnetizing current).
Since the current flowing from H1 to H2 is the same as the current flowing from H2 to H3, no line current is required on the H2 terminal.
Thus all three of the transformer coils are loaded, but there is single phase loading on the circuit feeding the transformer, because only H1 and H3 show line current (again, ignoring magnetizing current).
I believe that this work has only been theoretical, however in the last thread on the subject there were claims that Leyton built and measured this connection.
-Jon