Was anybody surprised when Ratchet used the term "heart" of Primus instead of "spark" in the series finale? The term that has been used as heart and soul(more heart than soul) of a Cybertronian throughout the series. Even Unicron's soul/heart was referred as his spark(which should be considered as the anti-spark).
I took it as more figurative " the heart of the matter" The center of primus as apposed to a big pumping heart.
