I have been thinking about this for a while.
Personally, I like that WotC seems to be stepping back a bit from alignment and that they were adding a "typically" to the alignment in the statblocks in the latest publications.
I think having a certain alignment would make sense for beings that are the embodiment of these alignments, like devils and demons, for example.
But I like it when everyone else has more leeway, I think it's also more interesting. Personally, I wouldn't put pixies in the same category (being the embodiment of an alignment, that is) as devils, for example. But I am not a pixie expert, that's just my impression.
So, with that in mind, maybe Larian has already taken into account changes that are made to the creature statblocks. I think it would then make sense to say that a pixie then can play harmless pranks, or malicious ones.
I must admit that I misremembered the exact phrasing of the lore check. I should have watched it again, but I was certain that the narrator had said mischievous and malicious.
I just rewatched the scene and the exact phrasing was "These fey creatures are infamous for their trickery - sometimes playful, sometimes malicious."
I know that mischievous can have different meanings, but if I understand it correctly, it has a more negative connotation than "playful". "Sometimes playful, sometimes malicious" sounds much more neutral, and I think I am ok with that.
So what we get from this lore check is basically that they like trickery.
(Yes, I sometimes manage to contradict myself or have a change of heart several times a day 😄)
