This is common misconception. Protected persons can use their home country passport and even renew it, provided that they do not travel to their country of origin.This very recent JR actually does mention that using your home country passport would be enough to lose status. In this case both used their home country passport to travel to their home country and neighbouring country. Unclear whether if person had only traveled to a 3rd country would have been enough but still a huge risk.
https://www.canlii.org/en/ca/fct/do...947&searchUrlHash=AAAAAQAJQ2Vzc2F0aW9uAAAAAAE
https://www.irb-cisr.gc.ca/en/legal-policy/legal-concepts/Pages/RefDef12.aspx