The effects of the Archfey warlock's Fey Presence feature and those of the charm person spell seem very similar; they both can induce the charmed condition on targets who fail their saving throw.
However, the description of Charm Person (PHB, p. 221) states:
When the spell ends, the creature knows it was charmed by you.
But the Archfey warlock's Fey Presence feature (PHB, p. 109) says
As an action, you can cause each creature in a 10-foot cube originating from you to make a Wisdom saving throw against your warlock spell save DC. The creatures that fail their saving throws are all charmed or frightened by you (your choice) until the end of your next turn.
The key thing is that there's no mention of the creature knowing it was charmed with Fey Presence.
RAW (and rules-lawyering) would say Fey Presence doesn't come with the side-effect of the creature knowing it was charmed. It doesn't even say you cast a spell, just that the effect does or doesn't happen based on a spell save DC.
Is the Fey Presence feature a non-spell, no-"hey you charmed me!"-hangover version of Charm Person?