Consistency rule
A rule at some prop firms that no single day's profit can exceed a certain percentage of total profit (e.g. 30-40%); it prevents passes that come down to luck.
The rule exists to stop "passing with one big trade," and it can also apply at the payout stage. A violation usually doesn't close the account, but it delays the payout or doesn't count the excess profit.
A trader who trades with a fixed risk percentage follows this rule naturally; it mostly catches people whose risk fluctuates.