There is a lot of information, that is copied from companies' web sites, unless you know for sure that it is factual, then you should not post about it. it only creates confusion for others that are trying to gather some kind of knowledge about VFD Drives and Spindles for their machine.
If you lower the power input on something like this, you end up with a very wimpy motor, so the whole exercise of having a larger spindle motor is not worth even trying, if you don't have the power supply to support it, now you said something in your post that would make this work, and that was to use 3Ph at 30A this would make sense, but not using single phase at 30A for the same install would not work out well.
There statement of 27% lower power is ridicules.