In my futile attempt to convince you otherwise, I cant confirm this difficulty bug
Well yes of course the more time you spent on the track, the higher the chance the AI will do a fast lap.
Usually you would lap fastest shortly after pitting, with less fuel and perfect tyres, so for the AI it would be after their last stop (1stop, 2stop, 3stop).
Though still, after waiting for hours I dont see any relation of AI difficulty to lap times or race total time. AI on average finishes at about 61minutes.
3 hours of easy -> 1:56,875
3 hours of medium -> 1:57:288
30+ hours of difficult -> 1:56,917
It is too random to quantify, the difference can easily be explained by different windstrength and direction.
And I dont see any 1 second faster time per lap like you said in the other thread
And then consider the AI isnt doing their fastest laps anywhere close to regularly.
In my old test of nearly all Gr.3 cars the fastest AI time I have seen would have beaten me in 26 races, yet the AI actually only won 2 races.
Giving up because the Supra is pulling away in its first 8 laps is wrong, because the Supra will lose more time in the pits than all other cars.
Giving up because of a single fast lap of the AI creates a wrong picture of the race in total, because it might just have been a fluke: AI with close to empty tank following other cars in a perfect drafting position at the perfect spot of the track and then overtake multiple times per lap - this is likely to happen after Medium Tyre AI has pitted and then catches up with Hard Tyre AI.