Actually there isnt any slap/blast from the shooter perspective on a 16" built. I wouldn't put it on a 10.5" built for the reason you mentionned thought.
Its a perfect brake for sports shooter and yes in a real CQB environement it would suck. But most people using this kind of brake are sports shooters who don't shoot within a team in an enclosed area.
Put it on a bolt gun and shoot it, then put on a brake like the Heathen and shoot it. You will definitely notice a difference.
I didn't think the APA Lil bastard Gen 2 brake sent any concussion/blast back to the shooter until I shot better designed brakes. Apparently I just didn't know better at the time.
Precision bolt guns and semi-autos are a different game. What's considered a good brake for semi autos doesn't necessarily make it a good brake for a precision bolt gun. The criteria for each is different.