Originally Posted by Khor Han Wei

Adding a data point here.

PVG - HKG on 8th March. Booking was 7pm but I arrived early to catch the 9am flight instead as I was on flex fare. Lady at the counter made some calls and was issued a boarding pass for Premium Economy. Proceed to the gate and found out was upgraded to J instead, all the way to the front of the plane at row 11.

On 10th, similar happened with flex fare, went to check in HKG-CDG at the machine and was issued a boarding pass for PEY at 32F. Went through customs and had a nice supper at The Pier and went to my gate, was checking my phone and I noticed the app showing me my seat have been changed to 23D. When I refreshed it, it suddenly switched to my original Y seat which was 40K, so I was thinking probably I have been op-down back to my original booking. Surprise surprise, when I was at the gate they bumped me up to J at 23D. F and J was full, and I suspect the rest of the plane as well.

So basically I booked Y but was bumped all the way to J on both the regional connecting and long haul flights from Shanghai to Paris. I am a GO member.