They have adopted a method that involves utilizing the estimatesmartfee 5 command. This base fee is then adjusted by a factor derived from an exponential function of a random number, specifically exp(random()*0.2-0.1). This formula introduces a controlled variability to the fee, effectively allowing it to fluctuate within a range of plus or minus 10% from the estimated smart fee. The intention behind this implementation is to avoid completely randomizing the fee while still incorporating a degree of unpredictability and variation into the fee calculation process.