Nope, not normal for me. I have downloaded many movies and series in HD (1920x1080). Some of the series I have been able to download in HD: Goliath, Billions, the Man in the High Castle (about half the episodes). There are many that are not available yet in HD. I am waiting for the fix to get them. Also, I have seen many episodes and movies available in 1280x720 as well (not just 960x540). I can only account for my experiences, other users in other parts of the world have theirs.
Edit to add: several of the movies on the "Home" page of Amazon Prime are 1080p for me, including: Hackers, Sister Act, Force 10 From Navarone....I could go on with many more.