Yes on bonding the nipple if it is metal. You pull in the service neutral and the ungrounded conductors.
If the PoCo grounds the neutral, you can usually get a fist fight started about using a metal nipple because that becomes a parallel neutral in some people's mind when you put in the MBJ.
OTOH 250.24(A)(5) really only applies on the load side of the service disconnect.
It is a question to ask your AHJ to see how he reads it.
