The bigger smell is no version control :D
Saving emails `onBlur()` is probably not a dark pattern.
Yes, there are some settings panels that automatically save changes, but I have never seen it for forms.
If there's an submit button on that form then that would be an even stronger signification to the user that nothing will be sent to the servers until you click that button.
As I said, it is distasteful but not a trick.