Which medium armors do not incur the speed penalty?
My concern is that the NPC Codex lists NPCs wearing breastplate with no armor penalty as opposed to those wearing other armors. (See the CR 4 Cautious Archer and CR 5 Adventuring Blacksmith for two examples of the discrepancy.)
Also, in the listing on the initial equipment page, breastplate reads as 20 ft as opposed to 30ft (no hindrance). I've read a few forums and it seems that everyone suggests wearing breastplate medium armor (to avoid the penalty, yet it still is listed as incurring the penalty?).
What am I missing here?