That's exactly opposite of what the connection diagram on the motor is telling him...
The diagram on the motor is typical of an IEC dual voltage motor, designed for 230/400V 50Hz in which the motor is connected in Y for the High voltage and Delta for the Low voltage. The 400V 50Hz connection will work fine for 480V 60Hz.
What I was saying is that this motor is connected as the high voltage when that picture was take. If the previous user though that it was connected for 240V, then were incorrect. The motor would have run, but the peak torque would have been 1/4th of normal. If the load was light enough, they may not have noticed and it was running that way for a long time. I've seen that happen several times.
Your reading of the nameplate is certainly different than mine.
I figured that when the nameplate said 230/460, 60 hz, and didn't say anything about 50Hz or 400V then that meant that the motor was good for 230/460, 60 HZ. I know really weird that I would think they didn't lie on the nameplate.
There is one other scenario: (pton alluded to this)
The pic I sent of the 12 lead is still good, but one of the wye points is broken off, the motor is connected for 230V and only running on half the windings. It would be an excellent 7.5KW 230V motor
Or you could be right.
At 60Hz it would be a 460Y or 277D
(edit) whoops, make that 460Y, or 266D