The treasure map chests will drop spriggan's, 7th legion, or whatever the light armor set is for that zone.
Each zone has three sets: one light, one heavy, one medium. The regular chests may or may not have one of those sets in them, the chance goes up with how hard the lock is to pick. The treasure map chests will always have one of the sets, but it's random which one you get.
Taking stealth away from the Bosmer is like taking magic away from the Altmer, making Nords allergic to mead, or making Orcs pretty.
Hi Garack, the treasure maps do have a guaranteed drop of one set piece from that zone. However there are three sets available to drop in every zone, so you only have a chance of it being the Spriggans set; the chest could also drop one of the other two sets that are found in Bangkorai. If I've misunderstood and that's not what you are asking I apologize, and maybe you could come back and clarify for us what the problem was.