That's a great point! The fact that we perceive differences between DACs, such as AKM vs ESS, suggests they aren't all the same. DAC measurements help us understand technical aspects like distortion, noise, and frequency response, but they don't always capture subjective listening experiences. While modern DACs may share some similarities in performance, nuances can arise from factors like implementation (e.g., power supply, output stage), which affect sound quality.
So, while measurements give us a technical foundation, personal taste and the context of how a DAC is integrated into a system can lead to differences in perceived sound. Testing different DACs allows users to make informed decisions based on both measurements and their subjective preferences.