I fly a Challenger 350 with Collins Proline 21 avionics and autopilot. We don't have autothrottles. We can use VNAV for descent and climb but we have to "be the autothrottle". As we also do RNAV approaches (LPV etc) and therefore VNAV must be engaged, I'd say you can use VNAV without autothrottles....
Now what the ATPL exams want is another thing, they are not based in reality most of the time.