i don't know why so many are so concerned with everything being so damned symmetrical all the time. who freakin' cares? that's probably why the rule of thirds exists anyway.
You're right, the rule of thirds does exist as a general rule of thumb when taking an off centre shot, and of course not all shots have to be perfectly aligned.
Sometimes a shot looks better purposefully off balance, sometimes a shot looks more interesting when the rules are broken, but sometimes a shot simply looks more photogenic when the subjects align nicely.
The eye works largely through pattern matching and focal bouncing at a sub conscious level. In this case it's simply more pleasing to the eye for those buildings to flow from the center of the image, it causes us to sub consciously notice the middle of the scene first, which is where the main subject (The girl) is positioned. Kind of like when you walk into a room for the first time and your eye immediately picks out a focal point - Could be the fire place, could be a large portrait, maybe it's even a rug. In any environment though, there's something there that your eye immediately recognises as the primary point of interest, and if the rest of the scene doesn't fit well around that central point, it simply doesn't feel right. Everybody has different views and nobody is right or wrong with those views, this is simply my own. Maybe I have a Feng Shui approach to photography ;-).
Here's a couple of quick crops to help show the difference between eye flow.
At first glance you may not notice, but sub consciously you'll pick up on the the girl first, because the buildings have drawn your eye towards her. This could be the case with the original image, but I find with this crop it feels more natural.
Now look at this second crop. The same alignment draws you to the girl, but then quickly to the other people in the image too. Most of which appear in the first crop, but here they appear more prominent. This is because the 4:3 format causes our eye to bounce around the similar subjects to the sides of the focal point, where with a 3:4 the eye was bouncing up and down. It's all on a sub conscious level so again you may not notice on first glance.
How the human mind works is a very interesting subject. Worth looking into the nature of eye's as a photographer, it helps with those first impressions of an image.