just a quick pajama experience update
NH 7 SFO-NRT -- asked and was explicitly told I could keep them
NH 879 HND-SYD -- reused the previous ones (no need for waste)
NH 880 SYD-HND -- left the pajamas behind in my half-asleep state
NH 8 NRT-SFO -- packed the pajamas away to have a set for home use after changing back into my clothes, and then after the seat belt sign came on for landing, an FA came by to ask for the pajamas and said that she was very sorry, but we were not allowed to keep them. Had to get up and extract them from my suitcase.
Bizarre inconsistency.