The general concept is correct but there are a few issues with the article:

- Specific RGB values always depend on a selected white balance temperature. If the WB temp is the same as the object's temp it would be white, not blue. If the WB temp were higher than the object's temp it would appear red.

EDIT: the article does say sRGB which implies a 6500K wb.

- "infinitely hot" is not physically possible. The Neutron star example is fine, that temp would be around 10^12 K

At that temperature virtually all of the emission would be in gamma rays, but emission in the visible spectrum would not be zero. Blue wavelengths would be stronger than green, which would be stronger than red so the color would appear Blue for any "normal" white balance temp (like 5500 K).