You can get double XP from Fine Leathers for certain pieces, specifically any piece that there's two of: bracers and cloaks.

Occurs if you physically get the bracers and cloaks from their respective rooms/containers rather than using the outfit command. I also just type wear all after collecting all the fine leather pieces so I wear all at the same time rather than piece by piece. Not sure if this also affects it or not and if it is by design.

I have no idea if that is intentional or not; probably not a terrible thing for new players to encounter, however.