If you think that the final report will be impartial just because the investigation is being conducted by the Russians you don't understand International Politics.
Russia could easily just ask for "favours" from the UAE in return for a less damning report. The UAE aviation sector (especially that of Dubai) is a major part of the economy, it will be seriously damaging to the image of EK and FZ to have a serious critical investigation questioning their practices. Right now Russia is in a bit of a corner politically and could easily use this report as a bargaining chip.