The 2 scenarios you present are unique and require separate ways of tracking.For any WordPress LP you can track that just like normal as long as you've installed your Munchkin code...
Couldn’t they have filled the form but then clicked the email/visit the page from their phone? If the phone was previously cookied it would keep the association...?
I don't believe so. I setup my webhooks to be a token payload, then whatever I trigger on that lead (or my own lead record if just general updates) and can customize the triggered ...
as long as when you create a new segmentation you also update that CDV.... and like you said it's not done regularly, so likelihood of forgetting to update BOTH is high...