I'm 100% subjective and perfectly fine with that. I extensively use the warnings you mention in my mother tongue (french) but tend to be more straightforward in (my bad) english. Apologies for that
To me, there's nothing like objective feeling in this hobby, neither "neutral" nor "well conceived system" on an absolute level...in the end, it's always a matter of taste. With time and experience, you learn to acknowledge those who hear like you...and those you're not able to share / understand the feelings. Looking at your system, I know we won't share the same feelings, as I find Jotunheim unbearably agressive / forward with HD600/650 (bit better with 650 BTW), let alone with what I consider as a forward sounding DAC like the Yggy.
First impressions I've read tend to more warmth and more thickness, I don't find Yggy "A" lacking both but would be pleased with more air / width, that's why I'm waiting for more impressions.
For the record, I listen most of the times to my music with e-stat (from SR-1 to SR-009) through a BHSE, and sometimes HD600/800 through Vali 2 / Magni 3. My Yggy is fed by an AES16 Lynx card, obviously in AES/EBU. I've listened to other systems (HE-6 / HD800 with EC 4-45 or 2A3 mkIV), and my comparative feelings stand, especially facing the AMR, less resolving and impactful, but more airy / wide / relaxed (whenever it has any meaning for the reader).
Ali