The rules exist to provide redundancy.
When you clean, presumably you're following rule #2 while you verify that it's unloaded, open the action, and either leave it open or disassemble the weapon. In either case, it's easily obvious that it doesn't matter if it's unloaded, as it can't fire. So you've got redundancy in that: first it was finger off the trigger and pointed in a safe direction, then it was checked to be unloaded and pointed in a safe direction, and then you checked it was unloaded and it's obviously unable to fire even if so due to the action being open or being disassembled. There is no step where there is a single point of failure.
The picture above requires only a brief memory lapse for an accident to happen, since there is no redundancy at play, you have no cross-check on human error. If you really can't think of a way for that gun to be loaded even with the main ammo stash being locked up, then I submit you're not thinking hard enough. The worst part is that the owner is over-confident enough to think it's safe. I sincerely hope that his first 'oh ****, I can make a mistake' moment ends well.
And since we're all gun-loving redneck idiots to certain folks, that picture ends up reflecting on all of us.
The picture wouldn't have made me cringe if the cylinder had been open, btw.
