I mean, think about it, just about every set release Po-Matoran had something different in story from the matoran they released with.
2001 & 2003: Hewkii- One of few characters to have a love interest.
2004: Ahkmou- Makuta loyalist
2006: Velika- Great Being
2007: Dekar- Transformed into Hydraxon
Coincidence? Most likely.