Hi Ted. Thanks for your kind words. I'm by no means close to a conclusion yet, but I've studied Mika a bit last week. I'd like to watch him more but here's what I observed so far: I noticed that sometimes it looks as if his elbow is slightly tilted in towards his body, but then other times it looks perfectly straight over the line of the shot. Like I said, I have a long way to go before I'm comfortable drawing conclusions but I'm thinking that possibly they are due to slight changes in his stance. When his elbow does tilt inward, though, it is very slight.
I also studied a video of Shane Van Boening --- which was shot from behind--- of him practicing break shots, which I found to be very informative. He was standing very sideways to his cue (facing his cue), which is what a lot of players do when breaking, but he positioned his chest over the line of the shot. The sideways stance twisted his hips out towards his cue, putting his elbow left of his chest. Based on that body position, his arm would have to have an outward tilt in order to clear his chest -- with the elbow tilted in. I'm not sure if I would call that 'natural' rather than 'mandatory' based on how his feet and body were positioned.
Still have more to study....