How can I watch Apple TV shows that I have purchased without an internet connection? (On a plane)

There is a massive discrepancy between Mac and iOS...

The TV app permits offline viewing of downloaded shows and movies on iOS, but not on Mac.

I am trying to watch on my MacBook, in the new TV app, a show which I have purchased and downloaded in anticipation of a long flight but it refuses to play without an internet connection.

I read elsewhere that it needs to be authorised only once, but this is not the case as as soon as the internet is cut, the show stops playing.

What gives?