I'm sure that's what he has on the back of his alternator. Did he actually pull the conduit off there to show there was nothing in it? How DID the wires get out of this extension on the back?
I'm not saying it's actually an electrical piece, i'm saying it's a conduit for the wiring.
Maybe some guy in the past couldn't figure out that to do this correctly: you have to remove the whole alternator harness along with the alternator, swap alternators and so forth and reinstall it as a unit (alternator and harness together). There is no cooling duct for the alternator.