The flagging system in the game for race difficulty is pretty... yea... well... sh*t. I am not even sure if it is based on PR alone. For me, it seems quite arbitrary sometimes.

Just take all the Hunter races, for example. Often flagged as hard, but then you overtake the opponent at 35% with ease. Sometimes, there are races flagged as easy, but it turns out you can't win them without a major car upgrade or with other tricks (for example wall bumps for extra airtime or anything comparable).

I have stopped long ago to take the difficulty flagging seriously. It's often pretty wrong. This is problematic for new and/or unexperienced players, as this flagging system is the only indicator for orientation.

My experience is: The last passed PR wall is in 99% of all races that follow afterwards - up to the next PR wall! - enough to win them. Let's say the last PR wall was 900. Then the races following it should all be doable with a 900 PR car. There are a few exceptions, but in general this works. At least, this is a better indicator than the flagging system.