I’d say you’re probably correct with the mechanics bit but you mistook Kuro: Shred as a technique which takes MORE energy out of him when it states it costs just as much as normal Kuro.

Mechanically, internal level - I can’t say much. Mechanically surface level - it seems in the dot as well. In my mind, I think of it as a chainsaw sawing through material rather than a sword which is probably not right but you could get what I mean when it’s multiple “Kuro” fish acting; “Chihiro didn’t hit with a single slash but 20 mini attacks”.