
Normally, playing through the game, when you get a purple staff, it's usually non-max in either the inherent HSR, damage, or energy. Still, it is possible to have the loot generator give you one that is maxed out in the inherents.
It's probably not uncommon and is likely caused by some rounding/truncation, but how often do these come up? Possible on whites and blues, too?
This one came from a nightfall free treasure, if it means anything.