If you were to photograph someone with a 35mm lens at 1 meter, you would have to view the resulting image at the same distance?
I think the argument people are making is that, the perspective would look natural IF: You printed the image lifesize (meaning the actual width of the head ON the image was the same as the width of the person's head), AND you viewed it from the same distance the camera was away from the subject when the image was taken.

Since it's unlikely that you would view such a large print from such a close distance, perspective would be perceived as unnatural.