The command is already placed before the camera is created, so it is strange that the flash shows what the camera sees. Another strange thing is that there is no flash in the first in-mission cut scene, where I use the same code.
I've tried putting the code in the init field of the player, but unfortunately the result got even worse. If you do that, you first get a flash of the player, then a flash from the camera and then finally, the screen turns black.
I thought the idea to use “Black In" was really clever, and it was also the only thing I haven't tried before. Unfortunately it didn't remove the problem. It's really hard to be sure, but it is possible that it made the flash quicker. Once again I've got the best result by putting the code in the initIntro-file.