We don't need the wikibase_item for Wikidata description editing. See T149220. Exposing the disambiguation flag sounds good to me.

Providing a counter to my own argument: The wikibase_item might be useful if we want to use it as an indicator if a related Wikidata item exists. Right now we would probably hard-code some logic in the clients to say only offer Wikidata description editing for main namespace pages. If we have QIDs exposed for all articles that should have them then we could just use that information. It'll take some time after this is deployed to have available on all pages, though. We may need to force a rerender. Another idea for using this is if we wanted to show a Wikidata item link in our UI.

formatversion=2 doesn't seem to work for this query: https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=pageprops&meta=&titles=Charles_Jones_(disambiguation)&redirects=1&formatversion=2&ppcontinue=&ppprop=disambiguation%7Cwikibase_item

"pageprops": {
                    "disambiguation": "",
                    "wikibase_item": "Q363381"
                }

The wikibase id would allow clients to do further queries, for instance to get the commons category.
It's a useful bit of information if we can provide it although I must confess I don't have any explicit use cases in MobileFrontend right now.
I've split the disambiguation task into T151241

Change 318163 had a related patch set uploaded (by BearND):
Expose Wikidata item ID number

https://gerrit.wikimedia.org/r/318163

Change 318163 merged by jenkins-bot:
Expose Wikidata item ID number

https://gerrit.wikimedia.org/r/318163