[_Tim_]

For info, I've run the AI turn a dozen more times to see if the same result occurs, and it hasn't created the strange outcome again. The DUKW got destroyed three times, twice with some survivors amongst the passengers and once with no survivors. The other times it is either unscathed or merely immobilised with passengers and crew staying onboard.
When there were survivors from the vehicle's destruction they survived the rest of the artillery barrage so I doubt that they bailed out and then got wiped out, the 76mm doesn't seem to have enough HEK to do that, unless at the very extreme end of the probability spectrum.

So the outcome that leaves the vehicle abandoned and no sign of crew and passengers is definitely an extreme event.

cheers,

Tim