The funny problem with this thing is very few people understand that it is illegal. There is a rail on that handgun. Forward grips go on the rails (intended for rifles, of course). So they say "cool" and slap it on, never knowing they are breaking the law. Which is easy to do, because no one would ever see this as being against a law. This law doesn't pass the common sense "this is probably against the law because an average person would think it should be against the law" mind test people apply when thinking about novel behavior. An average person just sees a piece of plastic intended for a rail and it never occurs to them something like that might be against the law.
I have even seen gun shops screw this up. I saw a Professional Arms (now Bushmaster) AR-15 pistol with a forward rail grip at Blythe's in Valparaiso, IN. Right on their wall, in plain view. I told the salesman that I though that would count as an AOW and he said that it did not. Next time it was gone and since then it has not reappeared. I guess they figured it out. And Blythe's is a pretty big full-service gun shop!