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. 🤦♂️
Your RPG StackExchange answer admits near the end “[…]as written, Tricksy Darkness has no effect because it doesn’t explicitly mention preventing nonmagical illumination, it’s logical to assume that it was intended to do something[…]“ The assumption that it should do something is the basis for the author’s claim that it blocks non-magical light.