How could anyone know in advance what kind of bizzaro answers Trump would give? Fake News! Hillary! Comey! Trump will simply not answer the questions in any coherent way. He'll lie to the special prosecutor because he is incapable of not lying[/I].
I'm sure he'll contradict himself multiple times, and some of those times, if he stands by his answers to the questions, he will inevitably be lying.
ETA: Even the Fox and Friends thing ... he said that "Our Justice Department, which I try to stay away from, but at some point I won't." He is telegraphing his intention to do something about the Justice Department. Though Trump does have the power to fire top appointees, any action he could take would arguably be obstructing justice.
No, the beauty is not knowing Trump's answers in advance. Given enough rope he will hang himself - not politically, necessarily, but legally. This isn't even about whether I like the guy or not. It's just Trump being Trump.