First of all, opening a new thread for that was unnecessary, you could have posted this directly in the topic or even better send a PM.
Car is definitely not stock, it accelerate way too fast. Then as
@zzz_pt mentionned, probably super soft tyres (in addition to aero and suspension tuning most probably), and as said by
@Stotty, looking at someone else's car on your replay might give very strange looking things if their or even your connection is not perfect. The lobby may have had boost settings as well, so with a bad connection, I can see how the game could actually activate boost even for someone who is actually first.
We can't make anything of that, although that does look weird indeed. What's sure though is that grip bug alone won't make anyone that fast in a BoP, fixed setup RH tyres race.
@Spurgy 777 I'll have you take a look at that, although I doubt your conclusions will fall far from mine.
@Famine maybe you'll want to merge this into the main thread.