I am not a copyright attorney so would not presume to know, however there are numerous forum threads about selecting copyrights and perhaps that question may be answered within one.
I see… iNaturalist might want to encourage users to share these observations with a different license than the photos then, as many Gbif data comes without photos anyway.
That way it would not be 100% lost for those who use Gbif…
The point is that a naturalist observation is not a personal, “original work”, it should not be a creation (we don’t don’t want something made up here), but only an accurate report of a reality.
So unlike photos, audio recordings (or books, blogs, etc.) I don’t see how it can be protected by copyright, and so the licensing term does not make sense for the observation part… maybe good to have the options to share with other sites, though.
I’ll leave it there, I got the explanation for my question, the Share Alike clause in this case, maybe you get my point too…