I'm just not seeing what obvious reality it highlights, so either I'm particularly dense or it's not in fact obvious. [...] But this is very much non-obvious...
The post is keying off of Think Like Reality.
Reality has been around since long before you showed up. Don't go calling it nasty names like "bizarre" or "incredible". The universe was propagating complex amplitudes through configuration space for ten billion years before life ever emerged on Earth. Quantum physics is not "weird". You are weird. You have the absolutely bizarre idea that reality ought to consist of little billiard balls bopping around, when in fact reality is a perfectly normal cloud of complex amplitude in configuration space. This is your problem, not reality's, and you are the one who needs to change.
Looking at the image it should be obvious that the colors do not look the same. This is reality. We think they should look the same even though it is obvious they don't. Once we find the right answer to why they don't look the same, the illusion should stop being bizarre.
If you find an explanation, return to the illusion, and still think the illusion is bizarre, than something is wrong. You fall into the category that EY is discussing in Think Like Reality.
I am convinced that most of what we consider to be fancy illusions will be considered obvious to future generations. They will look at this image and wonder why we thought it was so fascinating. When our optics system is solved it would completely ridiculous to assume that we would look at that image and think that the two squares should look like the same color.
But your post hasn't offered an explanation. And I don't, in fact, look at that image and think that the two squares should look like the same color.
A and B are in fact different colors, for a value of "in fact" which takes into account that the picture is a picture of something - a checkerboard. My visual system makes the correct inference, conditioned on the assumption that I'm looking at a checkerboard.
EDIT: what I should say is that I'm still surprised, knowing what I know about my visual system and how it works, when you tell me that the pix...
Today I looked at the above illusion and thought, "Why do I keep thinking A and B are different colors? Obviously, something is wrong with how I am thinking about colors." I am being stupid when my I look at this illusion and I interpret the data in such a way to determine distinct colors. My expectations of reality and the information being transmitted and received are not lining up. If they were, the illusion wouldn't be an illusion.
The number 2 is prime; the number 6 is not. What about the number 1? Prime is defined as a natural number with exactly two divisors. 1 is an illusionary prime if you use a poor definition such as, "Prime is a number that is only divisible by itself and 1." Building on these bad assumptions could result in all sorts of weird results much like dividing by 0 can make it look like 2 = 1. What a tricky illusion!
An optical illusion is only bizarre if you are making a bad assumption about how your visual system is supposed to be working. It is a flaw in the Map, not the Territory. I should stop thinking that the visual system is reporting RGB style colors. It isn't. And, now that I know this, I am suddenly curious about what it is reporting. I have dropped a bad belief and am looking for a replacement. In this case, my visual system is distinguishing between something else entirely. Now that I have the right answer, this optical illusion should become as uninteresting as questioning whether 1 is prime. It should stop being weird, bizarre, and incredible. It merely highlights an obvious reality.
Addendum: This post was edited to fix a few problems and errors. If you are at all interested in more details behind the illusion presented here, there are a handful of excellent comments below.