That is because there “is” a “projectile”. The wadding plug acts as a projectile for short distances out from the firearm muzzle. It is very light and loses velocity very quickly, but it CAN be deadly if you stand in the wrong place. Even the expanding gas from the muzzle is dangerous if one is too close. Neither, of course, compares to a lead, bismuth, or copper bullet or buckshot...but “I” would not put myself in the active zone.
Yes, the wadding is what killed Brandon Lee back in the 90’s during filming of “The Crow”. IIRC, they fired a squib, it got stuck, they put in a blank, and it ended up having enough force to enter Brandon’s abdomen and he died from the wound.
I just didn’t think the wadding itself would have enough force to cut down bamboo trees - those suckers are tougher than our skin!
Without knowing the particulars of what Stallone fired, I’ll reserve judgement on what happened.