Originally posted by GunsForBucks:

Wraiths have a chance to spawn at the swamp huts during the day or anytime.

This has always been in the game but I think it probably didn't work or was too rare.

After one of the patches the day wraiths seem much more common.

Kind of like how the wolf event was broken but this did work initially but just was super rare.

The way the wiki puts it those wraith/swamphut spawns were one time events like cave trolls.
From the wiki:
Anywhere in Swamps during the night time, despawn at dawn
Rare spawn point near abandoned huts in Swamps, also during the day time -One time

What it didn't say was if they were triggered the first time a player got near. In my case I'd been all over the only nearby structure, (a circular broken stone tower, not a hut) several times in the past weeks.

The Reddit posts also seemed to indicate that at some point wraith sightings in general increased noticeably. One thing I'm pretty sure of is the devs understandably enjoy tweaking stuff for us to 'discover'. Which I find refreshingly evil.