Backend translation of contents should show warnings related to defined fallbackType from Site Configuration
There are currently 3 types for Frontend: strict, fallback and free.
In Backend there are two modes: connected (translate) and free (copy), (and mixed if you count that).
Problem is that they are independent and very misleading to editors in certain setups. For example: if we define the fallbackType: free, backend still shows red warings if we mix both modes in backen - what is totally fine for the frontend.
Or we define fallbackType: fallback and create only free translated contents in backen - no warning, but in frontend no translation is shown but the default contents.
I think the warnings in Backend should be related to the fallbackType set.