Conceptually it is no different from pumped hydro storage. - for that they simply use negative numbers for pumping and positive for release.

I guess it's some technical problem with standardisation/tracking/reporting of the charging right now.

As/if Vehicle-to-Grid becomes more widespread, where you have highly distributed battery storage, it will be interesting to see if this will be publicly tracked.

Already domestic solar production is largely invisible ( as that mostly manifests in reduced demand ).

However I assume, in terms of managing the grid day to day, that such information is going to be important. ( eg if it's a largely cloudly day then that will be manifest as a rise in domestic demand ).