This (what you described) is basically how most optical illusions of the type of "look at this thing then look at this other thing" work, but this one is a lot

This (what you described) is basically how most optical illusions of the type of "look at this thing then look at this other thing" work, but this one is a lot stranger than most in that the effects of it can reportedly last for up to 3 months. I can't vouch for that directly, but I'm still seeing it an hour later and some other responses here have mentioned that they actually are still seeing it months later. Other optical illusions that rely solely on the mechanism you're talking about fade in under a minute.