The word "de" written by great calligraphers in past dynasties is missing a horizontal line. Why?

In ancient times, there were too many cases of many strokes and few strokes, especially calligraphy works, for very complicated reasons:

First, the information is underdeveloped, the writing methods are difficult to unify, and there are many cases of strokes increasing or decreasing or even variant characters.

Is the word "de" misspelled because it lacks a horizontal line? Although the writing of the word "de" has been standardized now, it is ok to have horizontal lines or no lines in calligraphy. But in daily writing, let's standardize it.