Hello!
If we change email for activation registered account too quiqly then enqueue_activation_email method of users_controller enqueue job without delay, so we got message to old email. May be it should be something that:
I do it through the user interface, by clicking on change email button for sending activation message after account registration. Paste other email-address at once, but receive message to old email. Same if click on back button in browser and type new email. If i do delay, then all is ok.