TB993TT, I cannot see very well the graphs, but is your 200-300kph run about 5 seconds slower than this one?
Despite that your runs I assume are made at much lower temperatures than in Kuwait as well, and they were two drivers on board, so one of the two cars is out of the 5% tolerance spec. There is a good 200+ HP there difference from 200-300kph in that case (ca. 5seconds). I don't have the answer, but in view of such delta, one needs to look further I think.
As far as rolling resistence, it is not very important, and it is linear vs. speed, unlike aerodynamic drag, so what you see above 200kph is the same as below 200kph, keeping aside all other factors such as tire expansion, heat, etc which should not be too far off between both cars.
Without getting too deep into physics, you can quite accurately calculate the impact of rolling resistence as follows:
Power to overcome rolling resistance = Weight (lbs.) x RR coefficient x mph / 375
The coefficient of drag for VERY smooth asphalt is 10 and for very rough asphalt is 22, data is widely available.
Poor asphalt: Power (BHP)= 3200 x 0.022 x 186mph/375= 34.94 Bhp
Good asphalt: Power= 3200 x 0.010 x 186/376 - 15.8 Bhp
This is to the wheels. Allow for 15% more to the flywheel due to parasitic losses and friction. As you can see the difference is not very important. This really has me confused.
All of the above, provided I am reading the right numbers of course!