George. You are looking at the wrong review. Your charts are for Stereophile PL Prologue measurements. The OP was clear that this post is about the
Dialogue Premium HP.
Here's the prologue measurements ...
https://www.stereophile.com/content/primaluna-prologue-premium-power-amplifier-measurements
Here's the Dialogue Premium HP measurements (apparently Stereophile tested the Integrated only, but amp is the same from what I understand) ...
https://www.stereophile.com/content/primaluna-dialogue-premium-hp-integrated-amplifier-measurements
as is easily seen - a vast difference in frequency response.
Here's the prologue measurements ...
https://www.stereophile.com/content/primaluna-prologue-premium-power-amplifier-measurements
Here's the Dialogue Premium HP measurements (apparently Stereophile tested the Integrated only, but amp is the same from what I understand) ...
https://www.stereophile.com/content/primaluna-dialogue-premium-hp-integrated-amplifier-measurements
as is easily seen - a vast difference in frequency response.