Phil Davis was a good help in Gus's performance but it's also and moreso Gus's hardwork but also physical gifts ( height, reach rame and weight similar to Jones ), youth and mental power that made him fight like this.
I'm a big shogun fan but even with improved TD defense Defense he would still have a huge leverage and reach disadvantage and would get tooled
Not to mention Shogun never showed any decent TDD while Gus's one was already good prior to the training with Davis