Simply put, Yor wanted Shin to kill and understand him. Shin then understood that you needed to use the Darkness to become stronger, but the Darkness can turn you mad if you’re weak. He then founded the Shadows of Yor under the name of Dredgen Vale. He kept the story of “the man with the golden gun” alive to stop fellow Shadows from going to far. He’s using the Shadows to look for strong guardians and kills those that go too far as Shin Malphur. He’s essentially a double agent for himself. Callum Sol sacrificed himself as a warning to newer Shadows to not go to far. Shin’s backstory is still true, but everything after Yor’s death was Shin living two lives.
Forget what you know and don't think about it too hard. That's what the writers have been doing.