When I originally saw that car I said the same thing and it actually kind of bothered me. I never asked the guy about it, I should have. The car is in no way factory-appearing in either color or engine bay, so if he was going for a factory replication that's out the window.
Seems kinda silly to invest all that money in the car to restore and build it and then go backwards and marginalize your braking system. It's such a simple thing to install. And you don't actually NEED disk brakes either, but the two-bowl MC is a basic safety consideration. To each his own I guess.
We now return you to our regularly scheduled programming.