All music is judged by the standard of instrumental absolute music (aka by the standard of Beethoven 5th) whether the music fits the category or not
In any case the only reason why I don't rate Harmonium higher is by the fact that a 13/15 is the maximum rating for an album after it first "clicked". I have to still think the album is great 6 months later for me to rate it higher. I think a 14/15 implies that the album has longetivity that needs to be tested over a period of time not just the immediate hit.
Fair enough it's not underrated but rather overlooked