Already said many times before, its because of the development. Synarchy is all the fury, aggression, and violence of the most extreme metal while being constructed in a linear form. If it helps to understand, Mitochondria has a similar goal as Synarchy in a different subgenre, only with worse writing and especially much worse vocals.
There is a gap. Between the underlying ethos of very extreme metal, and the higher aspirations of classical. If you notice, everything "progressive" in metal is based around taking away some of its violence, in exchange for more "depth" of writing. From ambient tracks, acoustic instruments, rock elements, etc. Synarchy reject this, it takes the depth of writing and applies it to extreme metal with barely even a hint of concession.
For instance Fas is an album with concessions, all the ambient sections that share almost no connection with the metal is a concession that they lack the talent necessary to bridge the two together in order to create the feeling they wanted to share. Its a shallow approach to depth that while it does indeed give the result one might be looking for, its also a haphazard irrational composition with obvious "here is the metal part" and "here is the ambient part".
Chaining the Katechon has no concessions really, but its repetitions without modulation or growth expose it for what it is: lacking ambition. Its content being "metal" as predefined by the social circles of music. One must have riffs, one must have drums, one must do x, and one must do y.
Ehnahre showcase how one can have no concession while still implementing ideas that go beyond "metal". Never once does there ever feel like there are "sections"
https://www.youtube.com/watch?v=Zud-xcs4qxE, only one seamless stream of music. Bands like Blood Incantation could take some notes on what real progressive should be.
