Yeah, you can see square-looking pixels on most screens if you display something with sharp aliasing. "There is no universal grid" is good to understand, but there are device-specific grids all over the place.
And all the examples that are ultra zoomed and/or showing antialiased font rendering obscure the pixels that are more visible in other situations.
That 0.01 to 0.04 degree range later in the article is big enough to drive a truck though. And you can see stairstepping at even finer distances.
In that case let's look at what reaching .01 degrees means for a desktop. At normal viewing distance, a 20 inch screen needs to be 4k, and a 30 inch screen needs to be 6k. Very few desktops reach the level where pixels are mostly hidden.
Ultra zoom approximates a pixel grid, but the pixel grid it approximates no longer exists (and arguably never physically existed, it was always a mapping scheme). We tend to think of pixels as square bricks, but even in the CRT era they were closer to 4:3 rectangles than squares, and that too was an approximation because phosphor beams were a fairly analog technology and hitting a square (or rectangle) grid was an imperfect thing, especially with something as excitable as light. That's why popular arcade emulators have been picking up CRT filters that bleed neighboring pixels over each other to more accurately rebuild the CRT experience.
That's part of what led to dithering being as much or more important than exact color matching. That's also what led to advances at the time in sub-pixel anti-aliasing such as the earliest forms of Microsoft's ClearType brand which blended neighboring colors to make perceptually cleaner font rendering.
As we've moved to solid state hardware the grid didn't get more exact, and sub-pixels became even more interesting, rather than less. Most LED displays are triangular shapes, not square grids, with red/green/blue LED diodes packed closely together to map a virtual pixel. (To my understanding some LED displays get even more complex with hexagonal or octagonal packing.)
The device-specific grids even more rarely today reflect what we would expect of a "square" pixel grid. (Or even a 4:3 rectangular grid.)
Square cartesian grids are easy to program with it. It's always been a useful abstraction, even in the CRT era. It's easy to forget that it was always an abstraction. Ultra zoom operates on the abstraction, not the physical reality. It explodes a cartesian grid, because that's mathematically easy (and the useful abstraction we like to program with).
(All of that is before you get to things like OSes and Browsers gave up on mapping the virtual pixel cartesian grids to physical "pixel" grids in real life because the "pixels" became too small, so most users see "16px" fonts as 125-175% expansion to keep fonts readable without magnifying glasses. Web Browsers have "lied" about the physical size of pixels since roughly the end of the CRT era and browser pixels are font-relative too, in which case the other font-relative measurements are often more useful simply for being "honest". Nobody really wants "pixel perfect" accuracy in websites, not even the designers that pride themselves on it and think it matters more than other characteristics like responsive adaptability to device type.)
> Ultra zoom approximates a pixel grid, but the pixel grid it approximates no longer exists (and arguably never physically existed, it was always a mapping scheme).
Square pixels are the most real on LCD, and most desktops are still LCD.
Also when I said ultra zoom there I meant the actual photos showing enormous pixels.
> Nobody really wants "pixel perfect" accuracy in websites,
As long as you're keeping the scaling correct, snapping to the nearest pixel is sometimes useful. I don't know if it counts as a "website" but I've coded webgl shaders that adjust to the real device pixels and look much better for it.
125-175 percent expansion also happens to be the range where being pixel-aware can give you the most benefit. Fonts look good at those sizes because the browser can render at the final resolution instead of scaling afterwards. (Except when macOS renders at 2x and scales it down so everything is blurry)
And all the examples that are ultra zoomed and/or showing antialiased font rendering obscure the pixels that are more visible in other situations.
That 0.01 to 0.04 degree range later in the article is big enough to drive a truck though. And you can see stairstepping at even finer distances.