After watching the AI for a couple hours on different aggression settings (it's too hot to go outdoors this week and do the useful things I should be doing), you can see the AI try steering too much, using too large of inputs, when around other cars which makes for car-to-car collisions and going off-track, reminiscent of PCARS 2 AI on their opening lap.
For demonstration purposes, I used the Skip Barber in groups of from 10 to 60 as I was mostly interested in measuring fps limits. Given enough straight (e.g. Le Grand Circuit), it's like watching restrictor plate racing with bump drafting and getting runs on the wad in front. It mostly works at 5 AI Aggression and definitely doesn't work at 25 or 50 AI Agression as they'll eventually just pile up in a big wad.
They also don't back off for braking zones, so the slightest extra slowdown by the car in front causes an impressive chain reaction collision.