From your screen shot, it looks like Arches is working as designed. Here's what's happening:
In your example, it looks like the provisional edit shown in your screen capture is in fact the very first time the Name card for the resource instance was edited. If you look at the message in the pink banner it says "This is a new contribution by a provisional editor". In plainer language, what Arches is trying to say is "this is the first edit of this card, and its been submitted by a provisional editor". Because this is the first and ONLY edit for this card, Arches doesn't need to show the information your are expecting on the right-hand side of the form.
Think of it this way: when a provisional editor submits a new tile, there's no way for any one else to see the tile until its been approved. So there will never be multiple edits to a brand-new tile from a provisional editor.
You SHOULD see provisional editors listed on the right side of a card when provisional editors alter an existing approved tile.
Hope this helps,
Dennis