Generally speaking, except for most strokes of seal script and other characters, the center is not omnipotent, that is to say, the use of flank has its reasonable factors and aesthetic value. The ancients said, "There is spirit in the front (that is, in the middle) and beauty in the next pen" (and New Interpretation of Linchi in Tang Dynasty). The strokes formed on the front side (the included angle between the strokes and the running posture is about 45 degrees) show a natural and smart posture. For example, Wang Xizhi's cursive script will naturally have wings in the process of writing. Of course, the flank takes momentum, and when the momentum arrives, it returns to the center. Related to this is the so-called "oblique front" (the stroke is T-shaped with the running direction, that is, the included angle is about 90 degrees). The strokes written by Pianfeng (actually swept out) are relatively thin, which is generally regarded as a sick pen in calligraphy.
However, it has been used occasionally in history, forming a more eccentric style. Beginners should, of course, proceed from fairness and practice hard in the center.
By the way, "drag" must be a sick pen. Never put off writing, or the strokes will be blurred.