Excalibur Umbra fills up his energy bar after killing a Sentient enemy

[zLuca374]

Even with no mods applied to him nor any other warframe bonuses, I can easily swing the Exalted Blade and abuse of Radial Howl to kill sentients pretty fast, because the entire energy bar refills after killing even just one sentients enemy.
If this is intended, then I can't find it written anywhere.
In the beginning I thought it could be a passive ability of the Umbra warframe, but there is no evidence of this in the "Abilities" tab under the Equipment menu in the pause menu.

[[DE]Momaw]

When you kill a Sentient Conculyst or Battlyst, they drop a bright orb on the ground. Touching this before it vanishes is a full heal and full recharge. It's not a feature of Umbra.