Misconception
The Primus has been mistaken as artillery being mounted on a Bionix chassis, and in the earlier days of development as a Bionix MBT variant. This was brought about by the fact that the UCVP (which the Primus was based on) bears a superficial resemblance to that of the Bionix and the fact that ST Engineering had indeed at the time been experimenting on a light tank variant of the Bionix.
Read more about this topic: SSPH Primus