It appears that article history/revisions are not a priority at this point for the core development team.
As a front-ender, this has left me a bit uneasy. Sometimes I need to be able to go back and retrieve prior versions of my posts and pages in Ghost. Here is one way to do that if you can access your Ghost files through a cPanel File Manager.
First, here is a screenie from the Ghost Forum Post . . .
To figure this out, I first created 10 versions of a new post Jen's First Post. I re-saved the post 10 times, each time after adding "Revision (number)." . . .
Second, in my cPanel File Manager I navigated to the location of the SQLite database generated by Ghost ghost-local.db under /content/data/ and downloaded that file to my computer . . .
Third I uploaded that ghost-local.db file on the webpage at https://inloop.github.io/sqlite-viewer/ . . .
Then, where the drop-down selector at the top of the page showed actions (12 rows) . . .
I clicked that, scrolled down through the items and selected mobiledoc_revisions (10 rows)
The two columns of interest to me are mobiledoc and created_at which contain the contents of each revision and the date/timestamp showing when each revision was saved.