A friend who has practiced calligraphy came in. Is it because he didn't practice writing and control his pen? Is it helpful to buy this pen-controlled copybook?

I suggest you write slowly to ensure that every word you write is stable, and then gradually speed up skillfully. There is a story: once, when Wang Xianzhi was practicing calligraphy at home, Wang Xizhi came in and suddenly grabbed the pen presented to him and tried to pull it out, but because Wang Xianzhi held the pen very hard, Wang Xizhi didn't pull it out. This shows that the way of holding the pen in calligraphy has a great influence on the pen control. I suggest that you can hold the pen with Rainbow fingers, which can effectively improve the control of the pen. It should have some effect on controlling pen copybook, but it is suggested to improve it by practicing calligraphy. To practice pen control, the most important thing is to keep practicing hard, and the written words will gradually stabilize.