It's kept it this way intentionally, yes, for mechanical consistency. For a different but somewhat related reason you'll find that
the Sigix Broadsword must be active in order to regenerate.
I've known about these and other things for a while (they were technically added long after the initial item set and mechanics were decided), but making special cases for certain items would be cause for confusion or misunderstanding in certain parts of the UI unless its complexity was further increased by adding multiple states to energy/resource-related readouts. I'd rather these values be static.
(One could explain the effect in logical terms as well, just pointing out the mechanic reasons behind not wanted to do it another way in any case.)