I'm a little over my head here and Evan (Waterbear) will probably answer this more thoroughly and accurately, but here goes.

The alkalinity and pH are related and will move together somewhat but they're not the same thing. For our purposes here, alkalinity is a measure of the resistance of the water to pH change; higher alkalinity will make the pH more difficult to change and vice versa. It will move down a little when you add acid to lower the pH but not radically and it will rise a little as pH rises. When you use Ben's technique for lowering alkalinity, the alkalinity will drop along with the pH but it won't rise again with the pH (or at least not as much) because you're aerating the water and releasing some of the carbonate that was in the water into the air.

I think (that usually gets me into trouble) that with your high alkalinity your water will probably tend to an always rising pH. But, if you don't have to add large amounts of acid often to control the pH and you don't have scaling, you might want be able to live with your alk as it is. If you find that dealing with the high alk is a big hassle, use Ben's technique to lower it.

There are a bunch of fascinating threads concerning alkalinity and pH on the forum here if you really want to understand this stuff. Look especially for posts by chemgeek and waterbear.