The calligrapher's pen-checking work is also a kind of creative work. The so-called pen inspection is limited by creative conditions, and the pen, ink and paper are not selected by calligraphers themselves. The purpose of marking "test pen" is usually to tell the viewer that this work is limited by the creative tools and does not represent my true level. Of course, some calligraphers are full of confidence in their works, saying that "trial writing" is intended to tell everyone that they have profound skills and don't choose pen and ink when creating.
Only on behalf of personal views, don't spray if you don't like it, thank you.