I understand your point as well. They could add the information similar to how they display the information for melding and item repair.
For example: "Desyntesizable: Weaver Lv. 25" instead of "Desyntesizable: Yes (weaver)"
From what I've seen, there are no items that show "Desyntesizable: No."
Edit: I just realized that "Item Level" is different than "Desyntesizable" level, since many high end vanity recipes are iLvl 1 and give high grade yields.