Support gem "Concentrated effect" on "Heral of thunder" don't boost dmg, but reduces area.

Not sure if this is intentional or a bug, but if you use the support gem "Concentrated effect" (+40% DMG / -50% Area of effect) on the skill "Heral of thunder" (killing shocked enemies makes subsequence attacks to release lightning bolts that dmgs an area around the enemy where it lands), the area gets reduced but without any dmg increase shwoing on the tooltip.


Tooltip WITHOUT gem:




Tooltip WITH gem: