On Hair: In Poser, if you load a new item from the Hair library it will replace any current item from the Hair library attached to the current figure - so if there need to be multiple parts the extras (such as ribbons or a skullcap) get put in the Props library. Hair may also be in the Figure library if is has multiple bones - the hair library is a special kind of props library, though some people did move their figure hair to it by changing the file extension. The Pose library is used for all kinds of settings - including material settings (the actual Material library wasn't added until Poser 5, and didn't support files to change all settings of a single item until Poser 6). So there is logic, if you know how older versions of Poser work.