The RC servo project is definitely not accurate enough for printing. It was just a fun project. It would need gears or some other mechanism to get the resolution up there.
Most delta 3D printers use steppers and a linear rail of some sort to gain the required resolution (and height for volume), but I bet you could use BLDC motors in a similar control fashion as used in stabilization gimbals for cameras on hobby drones and similar. I'm not sure if it would be better resolution than micro or continuous "stepping" or not...
