Hey Frederick -
Not a lot of people are aware of and/or use this feature, so it's not surprising you're not finding much.
Generally, the $expand option of OData is needed to show nested stuff (Entries) like information nested (a collection of associated "child" entries ) within the parent. In other words, my Order Detail entries are nested within the Order Entry, and I need $expand to get to that detail...
Tableau's OData implementation doesn't support using $expand. So, your approach of creating re-creating the view "pre-joined" and consuming it directly is exactly the way to go.