> There is the side note that they are owned by the same entity, but do regulators know that for a fact before they decide no to enforce penalties for what you are claiming is trademark infringement?

Yes. Yes they do. Absolutely, 100%, regulators know that Wingstop and Thighstop are owned by the same entity. They know this from regulatory and administrative filings, and they know this from the advertising that could not possibly be more clear that these are the same company.

Here, Rick Ross can explain it to you in no uncertain terms: https://www.youtube.com/watch?v=nTx4YuMa3cQ