The August release of XD is addressing an update for the asset panels in CC. That's not connected to XD as such, but its a general update in the sharing service that is part of the cloud concept, but since Adobe quoted that update as well in the XD release notes (see my first post) I'm addressing this issue here in the XD forum. I have not seen a specific forum for the asset section of CC.
The Assets panel the release notes are referring to is the Assets panel in the Adobe XD desktop app. It's not talking about the Assets section of the published design specs. The new feature works as expected in the desktop app, not the published design specs you view in a browser (as you've seen). I can see how that could be confusing because there is something called Assets in both places.
If you want to be able to reorder assets in the published design specs, you can create a feature request on the Adobe User Voice site https://adobexd.uservoice.com/ (or upvote the feature request if one already exists).