The purpose of the series if Bach was a cellist is to live the fantasy that everything Bach wrote, he wrote for the cello. It may also serve as a way for cellists to get close to Bach through works other than the six solo suites and the three gamba sonatas.
Cello Concerto in C minor for two cellos and piano. C minor becomes a powerful key in Bach's hands. It sets the tone of the composition, weight is added, and one can even sense how it directs Bach's thought-process. The present concerto exists as BWV 1060 for two harpsichords, but if Bach was a cellist, his prefered version would have been for two cellos.