That is a great tactic but, I don't think that's the reason Silva was doing it. Silva stood against the cage and let Bonnar implement his best game plan. It didn't work and it made Bonnar resort to his plan B which was try for the KO. Bonnar's back up plan is always Silva's first plan, striking. Hell, the fight ended, or the ending began, with Silva using Bonnar's plan A against him. He grappled and got the take down. Grappling for the take down was the only way Bonnar had the slightest hope of winning. Yet, it was Silva that ragdolled him around by the arm and succeeded with the trip. Then, Silva attacked and finished while Bonnar was getting back up.