You're assuming that yellow is permanently bound to a single particular wavelength. What if it's possible to rebind yellow to a different wavelength? What if it's possible to rebind purple to a single wavelength (rather than dual wavelength)? Color doesn't happen in the eyes, it happens in the brain.

Mirimir wouldn't feel surprised about the absence of purple if they understood color in the context of phenomenology (rather than engineering), which is the spirit in which the post was made.

I understand the difference you are pointing to. It's not a novel or interesting position, it's the default position. If you insist on binding colors to wavelengths, you probably didn't get anything out of the blogpost.