Please play these movies and let us know if they are really 4K, I have read in a home theater forum that this indicator is false, they actually play in HD.
Also, I have the same DC of Star Trek, (I do not have the 4K ATV, just the 4th gen. ATV), and it is still SD, so, please play the movie and let us know.
From the way Apple worded it, HD movies purchased through iTunes will get the free UHD upgrade. That might include HD digital copies redeemed through iTunes, but, not titles linked from Movies Anywhere. (Also, Movies Anywhere does not currently support UHD at all, if a title was purchased UHD, you can only play UHD from that source, not MA app., it will only transfer over in HD.)