Last year I had four flights on SQ on one PNR.

For two flights and I accrued SQ PPS value and NZ status points. The folks on the SQ forums say this is allowed.

However, for the other two flights I only accrued NZ status points. I querid why I didn't get PPS value this time and SQ told me that I was already credited NZ status points. I didn't fight it because I was never going to make PPS anyway.