This feels like a crazy question but a prefilled form still needs to be submitted for the "fills out form" trigger to be activated correct?
Specifically I have a form with a "contact me now!" checkbox (pre-checked) and then a few contact info fields (pre-filled if possible). The person does actually have to click submit for it all to matter right? Their record doesn't automatically get updated with the direct contact bit without them clicking submit right?
Yes. As long as the checkbox isn't already checked on the lead's record, the lead must submit the form for the Contact Me Now for the checkbox value to update/change and for the "fills out form" trigger to pick up the form submission.