Curious why it wouldn't start 'verifying' immediately on load? The fact that it runs in the background is really key--I'd hate to fill out an entire form, click the button at the end, and still have to wait around to submit.
The reason you wouldn't always want to start it in the background is if the user may not intend to submit the form (perhaps it's a form that is in your footer of every page and only a small percentage of users intend on sending it). Starting it on focus of the form is a good default.