There's a study that was done on that grinning emoji - and the miscommunication it can cause. I'm glad they fixed it: https://grouplens.org/blog/investigating-the-potential-for-m...
You know, the consortium also approved the slightly smiling face,[1] which should show content without being so exaggerated. Also I would never thing that your example in 2 would be expressing exhaustion, the mouth closes in the middle like the face is crying, not like it is out of breath. To me the weary face on iOS 11.2 looks like "poor you, i'm so sorry"
I guess one could argue that emojis are supposed to express the essence of an emotion to the fullest extent, but just like with color pigments it is nice to have dilutions.
(At least they got rid of that awful, awful grinning emoji [5].)
[1] https://emojipedia.org/google/android-4.4/smiling-face-with-...
[2] https://emojipedia.org/google/android-4.4/weary-face/
[3] https://emojipedia.org/apple/ios-11.2/weary-face/
[4] https://emojipedia.org/google/android-4.4/weary-cat-face/
[5] https://assets.change.org/photos/2/by/dr/IcbYdrlxwuCPHHJ-800...