It's the silver plating... in some applications it's fine, other times it can give you that splashy sound, which is emphasized/ringing leading edges. Copper quality will affect how much warmth (distortion) is added, UPOCC adds much less warmth vs typical copper and also has measurably better conductivity, from 1-3% depending... this doesn't sound like much but the results when used in an audio cable are pronounced. WE copper sounds different mainly because of the insulation type they used so the WE wire has it's own kind of tone. Duelund did this with silver, their silver wire is actually warm and laid-back sounding because of the silk/mineral oil dielectric.
Bliz, UPOCC silver does not have the same issues with edgy/bright vs conventionally manufactured silver wire, it's FAR different sounding... far better. It's still a bit light as far as harmonic texture, tone, image density... this is why I use the silver/gold alloy instead of just UPOCC silver. Wireworld and Siltech both try to compensate by using what's ridiculously heavy gauges of wire in their IC cables... 17g... I still use a substantial amount of silver/gold alloy and imo this results in a better sounding cables vs WW or Siltech. Unfortunately, it's very expensive but I think you'll find my silver/gold alloy wire is the best wire for audio use available.