Actually - you’ll have problems with that - because HubSpot doesn’t pass the $form argument to that callback like it does for onFormSubmit (this is very dumb and I had a lengthy chat w/ HubSpot support about it).
I would reccomend using onFormSubmit over onFormSubmitted - or if you plan on using onFormSubmitted - you’ll need to “cache” the $form in a global variable which would mean setting it via onFormSubmit and then referencing it in the onFormSubmitted callback.