I do think that in the instance that there was significant community spread coming out of a park, a lack of honest self-reporting might be overcome by people actively warning against visiting the park once we take the “Disney fans who wouldn’t want to damage a mega corporation’s reputation because it would ruin the magic” factor out of the equation. Which is to say that I think we’d know if the rate of community spread at a theme park was dramatically different than at retail stores.
But that just confirms what we already know: the virus is in the community, and there is no public activity that is entirely without risk, regardless of what the headlines want to say about the lack of cases tied to theme parks. And no matter how long a business is open without a confirmed case emerging from the location, that will never mean that a case could not emerge from there, and that’s going to keep a large-capacity industry like theme parks under close watch until next fall at the earliest.