In the Hiruzen fight Oro's Kusanagi was sharp enough to damage the adamantine staff Enma transformed into...that staff was hyped to be as hard as diamond.
Latter natures and Chakra flow were introduced. Specifically wind nature is said to increase cutting power...lightening release was shown to easily cut through v2 Bijuu shrouds, which seem to be even tougher than Hiruzen's staff...so had Oro utilized nature Chakra Flow, do you think he'd have been able to cut through Hiruzen's staff and Pierce the Version2 shroud of 4t Naruto?
Latter natures and Chakra flow were introduced. Specifically wind nature is said to increase cutting power...lightening release was shown to easily cut through v2 Bijuu shrouds, which seem to be even tougher than Hiruzen's staff...so had Oro utilized nature Chakra Flow, do you think he'd have been able to cut through Hiruzen's staff and Pierce the Version2 shroud of 4t Naruto?