I was reserving only for myself (emerald) in the PE cabin. I filed for a refund as soon as I paid the seat fee (3 weeks before travel) but did not receive any reply until the day after the plane departed and a refund was issued (due to the length of the flight the refund email was waiting for me when I landed at HND).
Ironically the cabin was almost empty - only 4 pax in premium economy and I moved to a different seat, but I wasn't to know that 3 weeks before the flight.
It is a shame there is such a hassle with the seat allocation in PE because PE on AY is probably one of the best premium economy seats and I would choose them for HEL-HND over JL (although food is better on JL).