I have checked on the latest revision of the FCOM NOR-SUP-ADVWXR-GROUND OPERATIONS IN COLD WEATHER CONDITIONS and it does only mention the possibility of having a thin layer of hoarfrost. The GTG mentions some powdery snow as well though. In our Company's Cold Wx Ops manual (EASA Operator, not Wizz) we do mention thin hoarfrost as being acceptable on the upper side of the fuselage, no mentioning of powdery snow. I probably think that the above scenario (again we did not observe what the crew did) is a bit on the edge. To be honest, from a human factor point of view, if the ground staff asks me twice if I am sure I am not going to de-ice the fuselage and I also see everyone around me going for a complete de-icing, then I might start asking myself whether I am the smartest guy in the room (or on the apron in this case) or there is maybe something else I am missing.