Writing these programs with separate focuses enabled us to make deeper, more comprehensive programs than other full-body mobility online programs.  The separation also provides options for individuals who only need to address either half of their body, rather than requiring them to purchase both.  We do realize that many people will want to train both, which is why we offer them together at a discount and have written instruction on how to combine the programs.
Additionally, these programs can be trained for a lifetime.  With this in mind there will be different periods where your fitness goals will shift, which can correlate with a change of focus on upper or lower body range of motion development.  For example, if you take up ballet barre classes, the Lower Body program might feel redundant, so you can shift to training just the Upper Body program through the duration of your barre membership.