I spent 5 years prepping at a chain restaurant in Ohio and my knife skills actually got worse over time, not better. Speed pushes you into bad habits that take forever to unlearn. A lot of wholesale shop guys I've seen can chop fast but they leave ragged edges and uneven pieces that affect cooking times. Real knife work is about consistency and control, not just how fast you can move your hands.
Oh man, I once worked a shift with a guy who could slice a case of bell peppers in ten minutes flat, but he'd leave the stem pith in every single one. Took me longer to pick out the white bits than it would've taken to just do it right from the start. Chef finally pulled him aside and made him watch a slow-motion video of his own hands on someone's phone. He still did it the same way.