Seems like a new config will be deployed to the NRT-SEA as per the press conference.
https://www.aviationwire.jp/archives/156541 (Japanese Only)
PE (total 35 seats) on rows 17-21 will be eliminated and will only be a 2-Class config on SkySuite (APEX) while Y would still stay 8-abreast.
JAL will do reconfig work on some existing 10 SS8 frames according to the report.