Here are all of the version exclusives, in case you wanted to check: https://www.serebii.net/ultrasunultramoon/exclusives.shtml
There are other differences, though, albeit small ones. Ultra Moon is set 12 real-life hours after Ultra Sun, so any gameplay during the day is at night and vice versa. There's also a couple instances of boss fights having different Pokemon between the two games, too.
I'm pretty sure that's all the differences-- no major story changes beyond the legendary or what time of day it is.