Why would you assume that bug is caused by Unity? If anything, the fact that it doesn't happen in literally every other Unity game should tell you it's specific

Why would you assume that bug is caused by Unity? If anything, the fact that it doesn't happen in literally every other Unity game should tell you it's specific to Hearthstone. And the fact that Hearthstone has a single codebase across platforms means that if Blizzard ever fixes it, it'll be fixed on all platforms.