A morph is just a series of new locations for the vertices that define the shape - when you apply a morph the vertex slides along a line connecting its starting position and it's morphed position. When you load an OBJ as a morph DS treats it as a list of new positions, the first vertex in the OBJ is the new position for the first vertex in the model and so on, which makes it absolutely vital that number and order of the vertices is not changed from the base when creating the morph.

HD morphs can work on the divided mesh, but we don't have the tools to load those.