I just realized that when I thought about the issue on my MBA as well as any laptop I have ever touched prior to it. The point being that when you touch the lid, the hinge doesn't move at all, but instead it's just the lid feathering back and forth (at least in my case). It's even the very reason why you call it "wobbling" instead of "opening wider". So it has to have something to do with the material involved into the hinge's connection, not the hinge mechanism and tightness itself. Which strikes me to be honest since the Surface Book's hinge seems to be constructed like a tank track with its metal chain link design. So it could be either the connection between the lid and the hinge, the hinge and the base or even slight tolerances within the chain links of the hinge itself that cause the wobbling.
Not that this changes anything (it might even make matters worse) but it definitely hasn't anything to do with the tightness of the hinge mechanism (on any laptop).
EDIT: I just made a GIF of this in action. You can clearly see that even though the lid wobbles, the hinge mechanism doesn't get utilized and keeps its angle (this was originally a 1 minute video of constant lid tapping which I just GIFed the last few seconds of):