The second word in the title of this CM is "Boundary". This is understood to be a boundary of a synoptic system (i.e. height contours at upper levels, e.g. 500 hPa) such as an upper level trough or an Upper Level Low. Consequently, a Baroclinic Boundary cloud is not situated at typical locations for frontal cloudiness, i.e. at the leading side of a trough.
Furthermore Baroclinic Boundaries are distinguished from stationary fronts and air mass boundaries.