The whole "bruised shoulder" thing really is the cymbal crash of dishonesty in the whole article. I don't think it's even possible to GET a bruised shoulder from a 223/556 AR rifle. Even a very, VERY light bolt action 223/556 like say, my Steyr Scout rifle - no WAY. I've let my 13 year old niece shoot that, and she's never once had a bruise, and she's under 100lbs ffs.
Someone should do a Youtube video testing various AR in a muscle shirt or whatever, holding it different slight differences away from the shoulder just to try and force it to impact and "bruise". I doubt it would. IF it did, it sure wouldn't be a big one. Shooting a single shot 12 gauge and holding it loosely - ya ok, but come on.
7 year old probably 50lb-ish girl shooting an AR carbine with a typical telescoping stock - she isn't pulling it in tight like a new shooter would do like the reporter who would be 3x her weight at least, and it's barely, barely pushing her, I doubt enough to bruise her through her jacket.
https://www.youtube.com/watch?v=sk-qAlU4ODM