Sounds to me like changing the “Cultivated” flag so it doesn’t affect the “Needs ID” is the best answer. That way flagging isn’t perceived as penalizing the observation. You can flag observations all day and be viewed as only adding to the data rather than relegating observations. People that don’t want cultivated for projects or their ID effort, can filter them out. People that want IDs of cultivated plants have a better chance of getting it.
Is a cultivated observation “Reseach grade”? Depends on the research. Having the flag is the important thing. Knowing about the latest trend in cultivated plants may tip off a new invasive species threat. GBIF should filter them out.
Looking for the win-win.