He puts those dark balls up there many times like that, and I have never been able to figure. Don't care much to either.
Notice too, he put all the solids together up-front, with stripes in the back. I have noticed he certainly has some weird racking peculiarities of which I think serve no useful purpose.
I personally don't give the slightest care to ball order, zilch. It can be dark to dark, light to dark, light to light.... I don't care at all. I guess if the lighting was really bad it may mean something and I may take action, never has happened though. If the guy requests something when I am racking for him, that is fine by me.
It actually reminds me a little of 8 ball racking: what i do is just put the 8 in the middle and the rest where they fall. Sometimes a guy will have a problem with that, and want some stripe/solid figurine pattern, I slide the rack over and let him have at it. I think people are clueless when it comes to the rack, and the patterns (or lack thereof) that lie within myself.
Really, the only thing that matters to me is the roundness of the balls with respect to the ability to rack them tightly. That is the only reason I move balls around in one pocket or even 8 ball (9 ball is TOTALLY different). Sometimes you get certain balls that seem to freeze better, and the guy wont want you to put them there (when racking for yourself). That irks me, but such is life. Ironically, the ball that people want in the front most often, the one ball, has in my opinion the most chance to be out of round and be less likely to rack well. This is why people need to get over their dumb preferences about this stuff, and use their noggen instead. Contrast is fine of course, but insisting it be the one ball is not.