You probably don't know much about filing, but there is no reason it would be any less accurate than CNC if done properly.

Also doubt this would affect strength, given the apparent thickness behind it, really depends on the interior, which is almost certainly also rounded for strength, and to prevent a week point for cracks to start.

Haha I was thinking the same when I read he hand filed it

As it is with any box, there is only so much material you can remove from the corners before it disintegrates into disconnected surfaces.

Filing vs. CNC doesn't make one bit of difference.

With a CNC you can make sure you'll get a uniform curvature.

You can get uniform curvature when filing. Ever hear of filing buttons? Or checking your work with a radius tool until you are in compliance? Stop talking about what filing can't do if you don't know anything about filing.