Sometimes that's the case, but usually on older guitars. I use 9-46 or 10-52 strings so I have an even heavier bottom, and on my guitars I notice a little extra pull over time on the bass side. It actually is quite desireable, considering the low strings vibrate in a larger pattern. So I set the action on the treble side low and relatively flat, and I get the little extra relief on the bass side for cleaner bass notes. Generally speaking, just the difference in tension alone on a standard gauge of strings won't be enough to pull a brand new guitar into assymetrical bow. If a new guitar is doing it, its more likely to be the wood itself.
If you imagine the difference between the tension on each side of the neck, you also have to calculate that the G and D are still very close to the center. So that variation has no effect. It's on the thickest part of the neck and right above the truss rod. But the A and B are farther out, and then the two E's are the farthest, so really you're calculating the difference between the two E's, and then "halving" the difference between the A and B. (you should probably more than half the A/B variance to include the neck thickness variable) When you look at it like that, its not much difference between the bass and treble side at all. On a 9-46 set its about 8lbs from a total of around 94lbs. So there's about a 7% swing toward the bass side. On a standard gauge of strings there'd be even less. My math is loose and could be off but not by a lot.