I flew DXB-MAD-DXB the other day on a J-Y ticket.
On the flight to MAD in J, it was very uneventful. Service lacked (as usual), no welcome by any crew (not that I care about it, but you will see my point in this post later). Pretty much a very plain flight. The crew were least bothered and just wanted to get done with their work.

I returned back the next day, thus had the same crew. Only this time I was in Y. The service honestly was impeccable. They immediately recognized the PLAT status, was escorted to my seat, SFS came by and introduced himself, got first dibs on the my meal preference, asked if I wanted any drinks from up front, asked if I was comfortable / needed anything throughout the flight. Had 2 seats blocked next to me. Not that all the above really matters (the seats blocked were nice - more room), but this just shows the inconsistency between cabins, with the same crew. I actually enjoyed my Y sector much more than J. It was like night and day.

Just makes you wonder if EK are trying to lure their passengers to fly Y rather than their premium cabins? It sure felt like that. To be honest, from all my years of flying, it seems like J is the new Y, and if you want great service, F is only the way to go (and Y at times)