In her video Dr. A-wht she was doing was telling the cashier to, "K-1", (a Target register code).
I doubt if I tried this the cashier would do what I said!
And I wouldn't want to risk someone's job.
I had a Rite-Aid cashier give me heck over a coupon, and I didn't even ask her to do anything! She told me that they had a policy not to accept "FREE"-anything coupons, and I told her that I would accept the policy, but I was curious about it since my coupon had a hologram on it and I knew where I got it.

I think the extreme coupon community is mad because either they can't get away with the scam, or because they get treated like scammers when they are not.