As MLB commissioner Rob Manfred has looked to innovate and improve pace of play, Rookie-Level leagues and Spring Training have been used as testing grounds over recent years for new rules and changes.
Perhaps most famously was in 2017, when MLB implemented a rule for placing a runner on second base when Gulf Coast League and Arizona League games went into extra innings. That was met with plenty of pushback, and though is now used at Double-A and Triple-A is unlikely to reach the Major League level.
Starting last season, Double-A and Triple-A saw a 15-second pitch clock implemented when runners were not on base.