I believe the 460V rating is because the earlier delta services were usually 230V so we could have a dual voltage configuration by either changing the motor winding connections or the taps on the pole top transformers series/parallel for delta 460 or 230.
With a grounded 480/277 they work fine. Ive never seen a 480V motor before, always 230/460.
I haven't seen a 460V delta service either for that matter. Most likely because the power company would rather keep 240/480 transformers in stock because delta 230V 3PH is not offered here anymore. The 240's are used everywhere for single phase setups.
No, it's for voltage drop. NEMA standards (nameplate ratings) assume voltage drop and are often different than nominal line voltage.
230Y/400V 50Hz is the European standard and why you see a lot of 208-240V 50/60Hz stuff, but 460V is nobody's standard. 460V = 480V - about 5% voltage drop. I haven't really seen much 201V stuff, but it strikes me as a similar NEMA rating which is OK within a wide swing of voltages.
200V is common, never heard of 201V, my shop has two Rockwell machines, 7" grinder & HD shaper w/ 200V 3Ø motors from the early/mid 1970's, they were both former school machines where 208V is prevalent.
Every voltage has two official levels; a "distribution voltage" and a "utilization voltage". The distribution voltage is what the utility supplies at your service drop, i.e. 480, 240, 120 etc. The utilization voltage is the voltage level to which the end use equipment is manufactured, which is purposefully lower to allow for expected voltage drop from the utility connection point to the end device due to wire length. So for 480V distribution, motors are made for 460V utilization, 240V becomes 230V, 120V becomes 115V and 208V becomes 200V. Nobody uses 201V, it's most likely a typo, rounding error or it's something from a place like China where the mfr has no clue what they are doing because they don't engineer anything, they just copy something else and they wrote down the numbers wrong when they copied it.
This differentiation between distribution and utilisation voltage is something that seems to be a US concept. In Europe distribution voltage and nameplate rating are identical and distribution voltage is given with a specific tolerance, e.g. 230/400 V +/-10%. On top of that you have 4.5% acceptable voltage drop between the service fuses and last point of fixed wiring, no more than 1.5% between service fuses and meter and 3% in the building wiring.
Manuals for end users then state "Only connect to the mains if the nameplate rating matches the info on your electricity meter!".
I had a job where we had VFDs right next to the 480V Service equipment so there was effectively no voltage drop. The manufacturer had to make custom drives for us because the normal 460V rating wouldn't tolerate the actual line voltage. Actually it had no problem with the voltage when it was 480...but when we started going above that (the Utility is allowed + or - 10%) the VFD started blowing boards.
I can't remember how many times they sent their standard 460V components before they realized that we actually knew what we were talking about when we specifically ordered 480V instead of their usual 460V stuff.
And no...we didn't pay them when they repeatedly sent us the wrong stuff and it blew up. GE now officially hates us.