When I've replaced master cylinders, I've been lucky to NOT need to bleed the brakes. Reason is that with minimal fluid loss, the fluid is heavier than the brake fluid, so any "air" in the lines will be at the top. Once the cylinder is filled and moves fluid, reconnecting the lines and some short and quick pedal depressions (in rapid succession) will usually put a negative pressure on the little air space in the lines, letting the new fluid replace it. The air then exits via the master cylinder reservoir. NO need to even get close to the wheel cylinders, which would only serve to pull the small amount of "air" up top down through the system, possibly causing more issues than it was meant to in the process.
In changing a line, pulling a vacuum on the master cylinder would work, too. Just that few people can do that.
At the assembly plant, they first pull a vacuum on the system via the master cylinder (via an overhead apparatus that attaches to the top of the master cylinder. Once the vacuum is stabilized, then the fluid all goes in at once. Same with the coolant and possibly the power steering fluid.
CBODY67
