Limiting and distortion go hand-in-hand. When a guitarist manipulates his gain structure to obtain distortion and increase sustain, he's turning his amplifier into a limiter. That Boost11 causes distortion should come as no surprise, but not all distortion is necessarily undesirable or unpleasant.
All limiters are capable of introducing audible distortion. Some just make it easier to achieve than others. My problem with Boost11, and why I don't use it, is that it makes it way too easy.
Limiters are used for a variety of purposes. Sometimes, you want as much transparency as possible. Sometimes you don't. Boost11 is for the latter case. That doesn't absolutely preclude it from a slot on the master bus, especially if used gently. But there are certainly better options for the majority of users in the majority of situations who just want to lift perceived volume without introducing noticeable distortion.