There are traffic engineering standards that describe this in every state and the country itself. However, that doesn't prevent a person with revenue generation intent from tampering when they install or maintain the signal, even remotely I suppose these days. If the same team that operates the things is also in charge of auditing the settings for compliance with standards.....you see where this is leading
That's no different than letting the police do the testing when you challenge their radar guns' accuracy. Have an independent review system. Then if someone challenges the RLC, you have documentation to back up the claim that the yellow timer is reasonable for that intersection.