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. 🤦♂️
The rules text says it creates an area of darkness, and with your interpretation, it doesn’t, which means your interpretation is wrong. Yes, the ability could be written more clearly, but the logic for a reasonable way for it to function follows pretty cleanly. Your interpretation is not RAW or RAI.
There’s a reply on RPG StackExchange that covers a similar line of logic to what I wrote above.
Remember that Fifth Edition D&D is intentionally not written with the same exacting precision as games like M:tG. The game doesn’t have an explicit definition of magical darkness, but it’s pretty clear that the intent is for magical to trump mundane (when it comes to sources of light and darkness). Even the Specific Beats General section says that most of the exceptions to general rules are due to magic.
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.