I think that Michael always thought that he could get away with lying under oath, not just in the Senate hearing, but in any proceeding that he would face. He knew the names of the people he dealt with directly - Frankie, Tom, Neri, Rocco - and he always knew that as long as those people were under his control, then he, at least, was insulated. Geary's question about buffers wouldn't add anything to what Michael already knew about his legal position.

I think that Geary was running interference for Michael on the public relations front. Michael would want the question about buffers to be raised as quickly as possible, so that his allies in the press and politics could all say, "He doesn't even know Michael", in answer to any questions.