EricF is spot on. The front shoulder action is in response to the core. Very important you don't try to start the barrel by directly using the shoulders .... something I see a lot of JV and young players do. They have a sense that the lead-shoulder pulls ... and they are actually somewhat correct ... just that they go after this directly rather than indirectly.
Agreed. This has been an issue with Maddie at times, as well as other young hitters I have worked with.