It is, no argument there.
However if you were to advertise a "doors-off" tour and tell the customers that they were free to remove the seatbelt after takeoff and move about the open cabin to take photographs, my guess is that your FAA Inspector would be all over you.
The harness was obviously a risk mitigation and the FAA knew it. Now they're acting shocked.
Yet everyone else who operates with harnesses/wander leads do not utilize fixed harnesses (ie screw type attachment without a quick release mechanism), nor are the people wearing harnesses typically walk up passengers (I suppose NYONAIR call them professional photographers but I’m pretty sure a judge will disagree).