Nice write up except for some electrical code violations , which I would not advise anyone to wire a VFD Drive and Spindle like this
For 120v this input wiring is correct but for 240v it is not to Code, the VFD Drive Output Wiring is also not to Code in either case
Wires must be the correct color White Neutral wire can never be used for 240v single phase unless it is covered at each end with Black or Red
No one in NA or any other country other than China, should be ignoring the 4th Pin this is for Ground and a 4 wire shielded cable must be used in your case from the VFD Drive U V W + G to the Spindle Plug Pin 1-2-3-4G
The 3 pin connectors also must be changed for a 4 pin connector so a correct Ground can be connected through the plug and to the Spindle Motor, the best thing is to never buy a Spindle that has a 3 Pin Plug these are for China only
This is a major Safety Problem not using a Ground Wire for these 3 Phase Spindle motors and a Code Violation