Nope is not, i made it the same layer inside photoshop:
As you can see, is just the merged images with a color overlay
EDIT: Also, here is the alpha layer inside unreal engine as a separate image over the other 2:
As you can see, they are the exact same size
EDIT 2: In fact, when viewing it in the widgets, the alpha mask applies properly, but the textures do not the white contour is the alpha mask being the right size