as to what ginge is on about:

ford garage calls up to ask him a question abotu fords
nissan garage calls him up to ask about nissans
audi call him up to ask about audi parts
etc, etc
so he knows lots about lots
the aa fella has probably not been taught about the wankel engine and is just guessing as to what the problems could be
we can all see the funny side, but who else got asked to top up a beetle engine with antifreeze when they were doing their training