There isn't any mention in the lore about a coin, so it's only a mechanic at this point I guess.
It can be a bit frustrating, but there isn't a single coin toss in combat that couldn't be evaded if you know the game well enough. For veteran players it's more of a choice. Like do you want to prioritize taking the enemy down fast and risk a coin toss, or play it safer, evade coin toss, but risk things going wrong in the long run.... that actually sound like a loss-loss situation now that I say it out loud...