One of the few things I really don't like about my Subbie is that it tries to help braking.

I'm all in for traction control and to some extent ABS, but braking hard and upsetting the car's balance when you don't need it is dangerous.

Is it one of those cars that alters the brake boost depending on circumstances?

That drives me nuts. When you put x amount of force into the brake pedal, you should know you're going to get y amount of deceleration. Don't double the brake boost just because you decided it's an emergency due to some opaque criteria.