This misses the most annoying part of the line wrapping which is how it interacts with GMail's "Undo Send" feature. If you notice an error in your email and click Undo, they bring you back to the compose mode with the hard newlines still inserted.

If you edit the email and send, they now add more hard newlines for where the new line endings are and you end up with a mix of tiny lines and normal lines looking like your email is written in free verse.