MotorSport France did the 0-1km in 21.2s @ 260 kph, very low temps. Is that so different from Auto's standard conditions of 21.3 @ 255? It's a little faster, sure but not so huge as the differences I will describe below.
The reason I think the 0-300 time in Sport Auto for the LFA looks strange is because
1) The SLS in the same test did 0-300 in 42.2, which is 5s slower than it has done in other tests.
2) The Jaguar XKR-S, which has a bit less power, also only 6-speeds, but weighs over 200kg more than the LFA can beat the LFA by over 7 seconds to 300 kph? (43.4 vs 50.6)
Here is that blue German press XKR-S, doing a 70-300 kph run.
Jaguar XKR-S im Test: Kätzchen oder Raubkatze? - SPORT AUTO
It appears to be the same XKR-S (same plate) as the one in the Sport Auto 0-300 test at Papenburg in 2011. In the published test, it did 200-300 in 30.1s. In the video of the speedometer, it appears to be slighly faster, about 26.7. If we assume some speedometer error, it might be similar performance, maybe shot in better conditions than at Papenburg? Who knows. In any event, the video shows a 200-260 kph time of around 11.2s. The LFA in the MotorSport France video seems much faster, closer to 9 seconds flat. How likely, then, is it that the LFA would suddenly be so much slower than the XKR-S in the final 40 kph spread, when it was already so much faster in 200-260? In the final 20 kph spread (240-260), I measure about 3.3s for the LFA and 5.1 for the XKR-S so the Lexus is still clearly faster even this late into the speed range. At worst, we should expect the LFA to be only merely as fast as the XKR-S in the overall 200-300 kph spread. That means around 26.7-30.1s and a 0-300 kph time of around 40s. The odds of it being some 2s faster in 200-260, still around 2s faster in 240-260, but then suddenly losing 9 whole seconds in the final 40 kph spread seems pretty far fetched.
The GT3 does have very good CdA (0.58), but the GT3 RS 4.0 does not. At 0.71, it's not all that far off from the LFA's 0.78. It still has a manual shift and 50 less hp than the LFA, yet is 9 faster in 200-300? Doesn't sound likely.
Another comparison to consider: In the Battle of the Supercars episode between the LFA and the R8 V10, the LFA proved to be just about as fast in a straight line. The two recorded very similar high speed figures.
Standing mile
LFA: 30.58s @ 167 mph
R8 V10: 30.64s @ 166.1 mph
Top speed
LFA: 184.1 mph
R8 V10: 185.1
Here's a video of an R8 V10 Spyder with manual transmission doing 0-300 in 43s by Sport Auto France:
The standard coupe has not a great aero figure, at 0.729. It's down on power to the LFA, probably suffers more drivetrain loss, weighs 100 kilos more. If the Spyder version can reach 300 kph in 43 seconds, then the LFA should be able to as well.