its behavior analysis , when you come out of tutorial island you have so little data to be analyzed so i think it works like a meter, every time it suspects something un-humane happens it adds to your bot percentage basically if your bot percentage goes above 50% you are a bot, so when you are out of tutorial island its so easy to reach 50% because there isn't data available to compare to so your bot meter goes up really high, but when you have an account that has a lot of played time its not easy to get that meter up cause there is a lot of data on that account.
This is how fairfight