I find this odd looking at it from a UK perspective although admittedly my experience is with criminal courts. The jury is the tribunal of fact. An appeal will consider if the original trial jury was misdirected about the evidence in front of it, including errors about the admissibility of evidence, but won't make further findings of fact unless new evidence has been unearthed since the trial. Evidence of FRAND known to the defence at the time of the original trial wouldn't, on that basis, be considered new. I suppose this arrangement allows the lawyers to milk the system but it seems to be a system ripe for reform.
OTOH if not raising FRAND in the original trial was to Apple's advantage why didn't PanOptis' raise it?