That brings up the age-old issue of "what does the real race driver actually know?" again, though. Now obviously I don't know your sources, but ideally they should have a very extensive sim background coupled with the track experience. A racedriver who has no experience with sims whatsoever has a very hard time actually judging the accuracy of a sim since he has no reference of what to expect or what is possible and how to relate to what happens on the screen to real world behaviour. Someone like that might be baffled just by having a car behave not completely arcadish, even if the physics were deeply flawed.
That said, I now watched the LFS segment and those ratings do seem kinda pulled out of thin air. Since they didn't use custom setups, the FBM should behave quite close to the real thing (it's mainly user setups that remove the front ARB for much better handling that 'ruin' the realism). I think they were simply bored by the sounds which makes the ride much less 'exciting' and that somehow influenced the physics score, or they had a crash physics explosion or something similar non-related cause a negative impact. About the gauges jumping around... no comment.