May you can have a look to profiles of the the players. I do so on Steam. Some Profiles are informative.
A lot of fast players have more than 1000hours played the game. A lot of them are really fast.
Some other you can also find in the daily, weekly and monthly challenges.
The Top 100 are also very fast.
Dont be surprised if you may meet someone in an open session from that boards.
If I find someone online in open races who has similar speed, than I , I try to invite them as friend.
Sometimes its accepted and sometimes I can race again with them together.
Free Time Trials leaderboards. I dont now. Its possible for me to hit some top 100 sometimes even top 50 Times. But could also be top 1000 ore more worse on some tracks ( Dailies best was Top 10 in comparison to that). Some times in freeride look for me that they are not from this world. Also seen some strange ghosts in the past.( Playing since launch of the game). But thats just suspicion, i dont want to falesly accuse somebody.
The dailies, and weeklies look more realistic to me.
I hope you get the cheaters, if there are some.
One question to PJTierney:
When a cheater is convicted, will there be the leaderboard entries of the time trials corrected/The cheater entries deleted?