Example: a half grapefruit, on a plate. The way I understand the guidelines, the proper way to deal with that would be to mark it as captive/cultivated, thus sending it to Casual. But next thing I know, it is “Life” because somebody added a disagreeing ID of “Human.” Now, if it was a human artifact, like plastic fruit or a fruit-print tablecloth, then “Human” would be appropriate; but there is an organism visible in the observation: the half grapefruit.
The same thing happened to an observation of a cup of coffee (with the coffee visible), and I think it was the same person who did it. There is a reason we have DQA; use it. Identifying grapefruits and coffee as humans could be construed as deliberately offering wrong IDs.