Musk got those fins of a ‘62 Cadillac El Dorado. BTW, there doesn’t seem to be any evidence of control surfaces or steering rocket nozzles. I seriously doubt that this thing would even be capable of accurately entering low Earth orbit. But then, He’s the engineering genius. Just listen to him for 10 minutes, he’ll tell you.
The three main rockets are steering rockets.
https://youtu.be/XVgEKBwE2RM?t=499
“This is for suborbital VTOL tests. Orbital version is taller, has thicker skins (won’t wrinkle) & a smoothly curving nose section.”