Again, we need Kal or someone like him, but here's the theory...I'd like to see the study from which that conclusion was drawn because my own experience contradicts this. Like most men, as I've aged, I have lost some sensitivity to higher frequencies. If I use an equalizer to boost the higher frequencies, it certainly does not sound harsh and unnatural.
Assume that you go to a live concert. Further assume that you have hearing loss in the 600-800Hz region. Despite that loss, your brain tells you that what you're hearing sounds correct, natural.
Now assume that we place a microphone between your eyes. That mic records a true representation of the event in terms of FR. If we play that recording in your room, which we'll assume has a flat response, you're still experiencing it in the context of your hearing loss and it still sounds natural to you. If we then EQ out your hearing loss by adding volume in the area of that loss, we're adding to the original event and, in theory, it should no longer sound natural.
Does that make sense, Rob?