Please be aware that J meal options are also a part of the F menu on all EK flights now. This wasn't in the past but I noticed it a couple of years back as EK started its cost cutting measures. So you may actually be seated in F but end up sampling a J meal. Apart from the caviar, I find the menu options pretty much the same. And lest I forget, several people here on the forum seem to fall head over heels over a bitter aerated drink called 'DP' served only in F.
As an aside, I was actually shocked after noticing how limited the choices were now in J on my recent DXB-BOS ULH. I have stopped eating on EK flights mostly and the options on EKs menu are going a long way in helping that cause. A far cry from what was on offer when EK first started its ULH to JFK and then again upgraded it with the A380. Been downhill ever since.