Shrapnel Ballista of Steel tooltip unaffected by chance to impale (character sheet is fine)

Shrapnel Ballista of Steel shows a 40% base chance to impale on hit, and speccing into chance to impale on attacks via my passive tree (e.g. Merciless Skewering is currently specced) does not change the impale chance displayed by Shrapnel Ballista of Steel's impale chance.

This does not seem to be impacting the character sheet, which currently shows the expected 70% chance to impale (40% base + 30% from the Merciless Skewering passive wheel)