I have seen several other pics of other panniers from the rear that show that they are not prefectly plumb vertically and some are not the same width at the rear as they are at the front. Which of these measurements makes them "splayed" I am not sure. Take a look at the recent rear shot of the top quality Holan bags on their racks in the pannier thread for instance. Both of them appear to be out of plumb vertically, but does that really matter in the end? Perhaps when they are loaded, they will end up vertical, but will that make a big difference? Look at the highly regarded Alt Rider crash bars. They stick out farther on one side than they do on the other, but they are quality bars just the same. SW-M racks may not be perfect for some, but take a look at others and in many cases you will also see features that are less than perfect, plumb or symetrical. In any case, if that bothers some, so be it, make another choice. Doesn't make a difference to me, as long as I have the bags I want, the racks I want, the bars I want, etc. . I think some brands, while being very well built and sturdy are too darn ugly for my tastes, but that's just me. We all have different tastes and criteria and we end up with different setups on our bikes, but they are each our own bikes, so if we're happy with them, who cares?
On the other hand, I could be wrong.