Again though, this doesn’t matter because of how global diplomacy between nations works. Thrall is speaking for the entire Horde as its representative. The entire council. That is how councils work. Each individual member doesn’t need to fly up to Nordrassil and offer their personal apology, that would be a massive waste of their time.
Ultimately you’re just inventing a fairly arbitrary reason to not count this apology and ask for more.
It absolutely directly benefits the Alliance because it stops the Horde from being highjacked by evil warchiefs and used to burn down cities again. Again, we’re discussing global super powers. Nations. Changing their government so that the Horde is a more secure organization is a very big deal. You’re downplaying the significance of it because it isn’t specifically how you wanted to see the Horde take responsibility for their crimes and take action to ensure it won’t happen again.