I'll explain it as I have come to understand the issue.
ED is a Russian based company.
Russia is currently involved in some stuff in the world.
The Russian government does not want Hi-fidelity modules of their Aircraft that are still in service, and will not give any technical data to my understanding.
The FF is a 29A. Currently Russia uses the M, K and Mig-35 versions. Possibly more, I'm not an expert.
In any case, Russia isn't worried if the west learn about a Mig-29A. They already got a bunch when East Germany, Poland, et-al joined NATO.
The modernized version would be like comparing the F-16A, to the F-16C Bl.52 (and there are still things on those A/C in game that are restricted/classified) Same bird on the outside, but inside a whole lotta things have changed.
That's how I've come to understand the issue. if anyone knows otherwise, I'm certainly not the authority on this.