Where there are missing fields, there's a red message that says the default value will be saved, but the presence of this message doesn't enable the save box, so there's no way I can see to ever save the default value. (It's not an issue in the case of the screenshot since there's another field to edit, but I had a previous case where the only "edit" was the missing field.
Also, when there's a missing field, it is not possible to see the help text.
Where there are missing fields, there's a red message that says the default value will be saved, but the presence of this message doesn't enable the save box, so there's no way I can see to ever save the default value. (It's not an issue in the case of the screenshot since there's another field to edit, but I had a previous case where the only "edit" was the missing field.
Also, when there's a missing field, it is not possible to see the help text.