At the very low pressures in the corona it is not clear exactly what the term “temperature” means. There are several different ways to define the term and they give very different results.
What other ways of defining it are there other than mean kinetic energy of the gas molecules (relative to one another)? Internal excitation? Furthermore, how different are the results? The corona was discovered (by an amateur) at radio frequencies, so at least the RF temperature measurement agrees with however T is being measured today. Please explain your post.
It’s a fair point but remember this is not a part of the universe in thermal equilibrium, so strictly speaking there is no actual temperature in this region, only an average temperature. It’s possible to measure that via ionization emission spectra, and that average is pretty well established.