Cinnamon and nutmeg do come from the same cinnamon tree.
However cinnamon and nutmeg are not exactly the same thing even though cinnamon and nutmeg come from the same tree.
Cinnamon is actually the inner bark of a cinnamon tree while the nutmeg is actually the cinnamon tree seed.
So they're similar but in reality cinnamon and nutmeg are different.
So if you have cinnamon you have the inner bark of the cinnamon tree.
If you have nutmeg you have the seed of the cinnamon tree so that is what makes cinnamon and nutmeg very different from each other.