The point seems valid: that digital noise will be per-pixel (as will noise from digital sensors). Whereas a scan of film grain is capturing literal grains which will not align perfectly with scanned pixels. The comparison image shows this.
one example: A. Newsom: Realistic Film Grain Rendering https://pdfs.semanticscholar.org/b791/566b0a38cc0269b1b7f9ad...
The point was that many editing tools offer noise generation that works at a pixel level. The author was explaining why those are unsuitable for the task. That doesn't make it nonsense.
The Wikipedia article for gradient noise[1] says:
> Gradient noise is a type of noise commonly used as a > procedural texture primitive in computer graphics.
A voronoi based vector codec could probably be close enough that people would struggle to tell the difference from film.
Having them represented as a circle or diamond wont change the point they were making.
On a ‘retina’ class display these square areas are explicitly smaller than the resolution distinguishable by your eyes.
Any sharp edges or corners you think you can discern are your mind reconstructing an edge from a series of neural samples on your retina that are the sum of the output of various sub pixel blobs of red green and blue light that focus on that particular cluster of cone cells.
That is what we call a pixel: the smallest representation of a point of full color.
But, none of this matters for the point they were making.