If the reason to know priority is to determine who gets an OpUp, isn't that more of an academic exercise on SQ? In my experience of nearly 18 years of J flying on SQ, I've had one instance where the leading steward came to me in the upper deck of a 747 before departure and quietly asked me to come with him, where I was given a seat in F.

I suppose it's possible that SQ doesn't have a real-time priority system within PPS levels that's based on PPS value that they use for OpUps or other purposes. They could use time of check-in, fare purchased for that flight, etc.