I was surprised to see the TCE Summon Fey spell got reworked for the new PHB. I was very surprised to see they realized the Tricksy Fey needed the darkness buffed. I was even more surprised to see they did not understand why the darkness needed to be buffed. 🤦♂️
But Umbral Sight works with normal darkness too, and if it doesn't prevent magical or non-magical light from illuminating it, people don't have to rely on darkvision to see them in that magical darkness (if it's illuminated by anything). At least the Hallow darkness effect prevents illumination, so that does work for Gloom stalkers, but this is quite literally useless.