Bookworm
No, that's the whole point. A lower probability of icing in the cloud that is producing the snow/sleet, because the presence of snow is an indicator of glaciation and the probable absence of supercooled water.
The weakness in your argument is the use of the word probable here - the fact is that to produce snow in the first place you must have supercooled droplets so that the water can evaporate from the droplets and form ice crystals on the freezing nuclei (the Bergeron-Findeisen process).
So, since both will exist in varying amounts depending on the conditions you cannot say with any certainty that the snow cloud will be a lesser icing hazard than the no-snow cloud.
The simple point is that the higher icing potential comes from clouds that have high supercooled water content before glaciation, not the ones that are already glaciated and shedding snow at high rate.
again - you talk about differences in potential which is probaby true but is not the hard and fast 'snowing therefore no icing' rule that you advocate.
And then your capitulation
There are no certainties when it comes to icing, and any flight in temperatures around freezing is going to have to pay significant attention to conditions.
which is what Shy and myself have been trying to get through and why we dislike ridiculous simplifications llike 'it's snowing so there is no risk of icing' which may influence the less experienced on this forum.