Good point and I have considered the mess factor, Maybe I'm reading the paragraph wrong, I got to thinking, is this for first responders, not a built in system ? Honestly the problem I'm having is the cost of a Halon system , 500 bucks and up. Yeah I'm cheap!
However if the engine is on fire , and you dump a dry chem bottle , your'e pretty much done for the rest of the event. so plenty of time to clean up when you get the mess home .