You’re not the only one seeing it. I am beginning to think that there were some considerable changes made to the interface to speed up game play. This is a definite example of it. A similar one is where collecting all of your food from farms makes the food counter update unpredictably, but accurately. Another one that has stood out to me is when raiding against a team with Margaret on it. She has a lengthy animation on her special. If she fires her special on the same turn that someone has a slash attack, the hero will perform the slash attack before her special animation finishes. Unfortunately, it looks like things aren’t in sync. In order, but not in sync.
Related, I’m pretty sure that I was fighting a boss and its turn counter updated to S, but it didn’t use its special on the following turn. Maybe it updated to 5 and my vision wasn’t clear, but I’m pretty sure that’s what happened, especially since the mana bar was full, which is a more obvious indication.