This sounds reasonable, but it doesn't seem to reflect reality. The biggest reason that shows are region locked and/or removed from streaming sites are licensing deals, not technical reasons. Movie and TV production companies are the ones pushing for the region locks, and the ones selling limited distribution rights to streaming services.

So, while you are right that video streaming is much more costly than audio streaming, I think GP is overall more correct about the reasoning being production costs rather than anything to do with distribution.