Nemrod, the same way people cannot assume that tanks will always be low in the water, you cannot defend it in absolute terms, because for some people they still are low in the water and still cause problems.
This one is so low it's past the butt and clearly pushing the diver hips down, which is not good for trim.
When the tank gets lighter, if only connected to the BCD at the top, it can have the opposite effect and act as a lever.
And yet, it's possible to have it not hitting the head and not going down past the butt in a more central position.
Of course that we don't know how these tanks look on the surface and maybe even for the third diver it could look as it it was too low. But this is to show that there are too low tanks even in the water. They may be because of trim, as some people mentioned, but I think there are better solutions, because of the person's dimensions (it's possible to get shorter 12 l steel cylinders) or because the divers don't know better. And I think it's relevant to discuss this and acknowledge that it's not always been done correctly. At least divers should question how they are setting up their cylinders and see if there are reasons or not, what are the implications on their trim, finning fining, comfort, etc, experiment a bit and see what's best for them.