The use of single-phase three-phase generators is excessive. It is suitable to use 220V between current and zero, and it is also suitable for long-term use, but the current cannot exceed the rated value. For a 30KW generator, the current cannot exceed 46A at a voltage of 220V, or less than 1/3 of the total power. You think it's a loss or not.
Three-phase balance means that the current of the three-phase live wires is the same.