Why is a difficulty of 35 in "Series" so much harder than "Grand Prix"

I can't be the only one with this problem. 

If I go into F1 23 > World > Grand Prix set up a race with a difficulty of 35 - it's super easy. I fly by the other cars, no problem, last to first totally doable. 

But if I go to F1 23 > World > Series (the races you have to complete to unlock the challenges) it's near impossible, feels like an AI of 100 even though the difficulty level is locked in at 35.  

There is an enormous difference even though they're both set at 35. I don't think I'll ever be able to unlock them. What is going on?