That is the way that custom builders do it. It makes sense too. You fab parts, fit them, then pull them for paint.
What do you do when you have a running, driving car? I guess you can't make an omelet without breaking a few eggs. It IS daunting to take a running car apart though. My Charger was running during body and paint. We removed all body panels that could be unbolted.
The TV car show builds often show the order of Drivetrain, Body and paint, then interior.