Maybe there's different cognition at play between scrawling a sentence and taking the time to sense the rollerball moving. With the latter, letters take on a more, um, "architectural" font (for lack of a better term).
Personally, I think good training involves transcending the duality of "scrawling" and "writing carefully," finding a balance between speed and accuracy. For a baby, everything they see appears to be "moving rapidly without error." As one’s abilities improve, I believe it's possible to achieve both simultaneously.