I fear this may be a result of P-4828; not possible to create attributes of same name as parent in child object perhaps?
Anyway take the standard Asset Management\Service Window. In there is the "Service Description" field which is the Description field from the Assent Management BO. Try and find that attribute in the attributes tree. I'm assuming it's because CI inherits from Asset...?
I noticed that the end user window wasnt using the same description field and when I tried to add it it wasnt available. As a workaround I copied the full window that did have this field on it and saved a cutdown version for the end user.
We should be able to access this attribute from the treethough or is the OOTB wrong to use this field.
Could there be wider issues here of fielsd we can no longer access post 7.5? It might have been in 7.4 too but i'm sure i would have noticed this.