I don't disagree with you... while it's a minor problem, part of the excitement in pack opening is finding out if you got a legendary, and when you do, which one it will be and if it'll be golden. If the game tells you you not only got a legendary but also what class it's for, it kinda takes away a lot of the fun. Not an issue that needs to be addressed right now when there's still a ton of game breaking bugs going around, but probably something that should be resolved in the future
It does not tell you what class it is for. In OP‘s example it could have aswell been a neutral legendary plus some other druid cards in the pack.