Yep, NASCAR more upset with the bad optics, than the actual occurrence.
When it's that obvious of an intentional spin and then Dale Jr. immediately confirms your suspicions on a national broadcast, someone probably had a talk with Junior about not saying that type of stuff anymore too.
Fine and penalty might make some driver's think twice about pulling this in the future, or just make them better at hiding and clamming up about it.
I'm not sure how to stop it, but no special treatment and you don't need a confession, I don't think NASCAR is up to the task though, and I don't think NASCAR wants to discourage cautions either.