Focal Arche has been discussed many times on these and other forums as to how it “matches” with each Focal headphone. It may have been known to some before, but there was still confusion as to what the mechanism was exactly, and it was finally confirmed on Headphones.com’s own livestream with Focal reps not too long ago.
The answer is: it is impedance matching for each set. Nothing more, nothing less. It’s no gimmicky DSP or anything like that.
Focal knows what impedance is ideal for each of their sets so I would trust them on that.
And if it’s not desired - as mentioned - it can simply be used as a regular (but well implemented & performing) amp and/or DAC.