D2.321 is all about the fire of a bypassing vehicle so I think you are on the mark. Indeed, D2.321 refers not to a CA, but exclusively to a bypassing vehicle's TCA. No TCA, no applicability of the exception, yes?
RB says the berserk unit does remember where its original target was "should the only Known enemy unit no longer be in his LOS in the interim."
Not clear that addresses whether the berserk unit can remember anything other than the desire to kill if someone new comes into view when it can't see...
A15.431 does say if "closer (in hexes)". But as the original enemy unit is no longer a Known enemy unit (it's not in LOS), isn't any enemy unit that the berserk unit then sees a closer Known enemy unit then the original unit?