Upekkha,
Please allow me to make one final comment:
If to you it is clear, or becomes clear,that whatever an Arahant is made of cannot be defiled, in whole or in part,then words, and the meaning of the components of those words, is of no importance. The ‘vinnana’ of an Arahant IS undefiled, just because the ‘vinnana’ of an Arahant CANNOT be defiled. He has gone through all four stages of the Path, He is perfected: ‘Birth is ended….’ How can there still be any trace of defilement in Him?
All the trouble I myself took going into the ‘vi’, defiled, tainted etc was just trying to find a fitting interpretation of how the word ‘vinnana’ could apply to an Arahant. But I was never in any doubt, in whatever way the word ‘vinnana’ may apply to an Arahant.
Metta to all