Crown of the Pale King affix does not do what the tooltip says

The unique "Crown of the Pale King" has an affix that reads:
"Thorns Damage is triggered by all Hits"

Contrary to expectations from this ability text, thorns damage is not added to hits struck BY the character. It seems that, from this text, thorns damage should be triggered by all hits not just against the character, but also made by the character (adding thorns to attack damage).