Something that isn't clear to me: Why, exactly, is it so much faster than even its own build tool(swc)? In other words, what's speeding up here isn't build spe

Something that isn't clear to me: Why, exactly, is it so much faster than even its own build tool(swc)? In other words, what's speeding up here isn't build speed, but the ability to download the updated changes. Right? Or am I wrong?