Your understanding is wrong. Every one of your scenarios, where you are a second shooter, where your assistants shoot for you, artists assistants etc all sign away any rights they might be granted under the law when they work under contract to the employer.
So take these scenarios, your camera is stolen but it is found a month later, some funny guy took it on holiday with him and took photos of a garden ornament all over the world, do you own the copyright? Of course not.
You leave your camera as a remote camera in the woods with a trigger, somebody moves it and takes a different shot to the one you had set up, do you own the copyright? No, you do not.
You leave your camera in the woods by accident, a branch falls on it and just presses the shutter button, do you own the copyright? No, you do not.
You leave your camera in the woods with the intention of wireless remote shooting, a child comes along and moves your camera and in the process pushes the shutter button, do you own the copyright? No you do not.
Take the last scenario and exchange a child for a monkey, you still don't own the copyright, you did not frame or take the photo.
Somebody does not have to own the copyright, an image can be copyright free, that is what Wikipedia are asserting, the image does not have copyright on it so they are free to reproduce it without restrictions.
THIS ^^^^^^^ +10
If you don't frame the shot, then you don't own the copyright. Personally, I think the macaque should own copyright, but then I'm biased in favor non-human primates.