More on the Sony USB Connector
I noted that although the mini b plug has 5 pins the standard plug on the other end has only 4 so I did some internet research and found a web site that describes what is in the usb connectors.
This extract from the web site may explain things:
Pin x of mini-USB connector may be not connected, (may be) connected to GND or (may be) used as attachment identification at some portable devices. This pin is numbered x here due to historical reasons.
Pin Name Cable color Description
1 VCC Red +5 VDC
2 D- White Data -
3 D+ Green Data +
x ID May be N/C, GND or used as an attached device presence indicator (shorted to GND with resistor)
4 GND Black Ground
This suggests that the Sony lead is using the x pin for recognition purposes
This will be my last word on this subject