OG UI referring to disabled Field UI

With OG UI enabled and Field UI disabled, I can make a content type be an OG Group or OG Group content. However this isn't reversible. The checkbox is locked and some help text refers me to the non-existing 'Manage fields' tab which would only be available with Field UI:

To unset the group definition you should delete the "Group type" field via Manage fields.

To unset the group content definition or change the settings you should delete the "Groups audience" field via Manage fields.

However Field UI is no dependency of OG UI.
Possible solutions would include:

1. Make Field UI a dependency of OG UI
2. Unlock the checkbox, so the OG fields can be removed just by unchecking the checkbox
3. Show this description only if Field UI is enabled so the checkbox is locked and there's nothing we can do here
4. Refer to the admin who needs to install Field UI to remove the OG field

Actually, only the first two options seem to make sense, and I'm leaning towards the first one. If a field gets added, it must be removable again. Removing and recreating the whole content type certainly isn't the better option.