I'm unable to find a way to select/download SD versions of purchased movies.
1. iTunes "Downloads Preferences" for HD and high-quality SD videos are both unchecked, but "default" remains as HD.
2. Within my Library I change the video quality to Standard Definition (SD), but movie remains as only HD option.
iMac with Retina 5K display, macOS Sierra (10.12.3)
Your suggestion is what I was accustomed to, but the new iTunes actually changed that to a "Play" option. I found the way to download the SD version is now via the iTunes > Store> Purchased > and unchecking "Download HD When Available" (Which I've never had to do before).
I believe that the video quality is selected at the time of purchase. You can indicate your preference in the Download Preferences of iTunes. The Video Quality menu item is only used for playback in iTunes on your Mac. It doesn't alter the file for downloading.
iTunes 12.5.5.5 SD download issue
