Hokuto no Ken was Mar 2006-Oct 2008.
Kara no Kyoukai was Jan 2007-Aug 2009.
Not that far off and done with an overlap.
I disagree with it regardless, but don't know why you would split after KNK (but then also use it as an example) for a thesis that "OSTs for male heavy shows aren't as good as for the female ones". You cut off over half of Kajiura's discography from it.
You now only have
Madoka Magica(not-Iwanami), PriPri and I guess Heaven's Feel
vs
Pandora Hearts(not-Iwanami, also pre-last KNK), Fate/Zero, SAO (on/off for 8 years now), ERASED, Zaregoto(not-Iwanami), El Melloi(not-Iwanami)
There's LORD and Demon Slayer for the 15min medley, too, I guess.
And... I just don't see the female-driven-shows=better/male=worse correlation but if thinking that works for you...