Long sentences refer to sentences with complex structure and many words; Short sentences refer to sentences with simple structure and few words. Short sentence structure subject+predicate+object long sentence is based on short sentence with adjectives.
After the Song Dynasty, it can be said that long and short sentences are aliases of words, but in the Northern Song Dynasty, long and short sentences are the real names of words. In the Tang Dynasty, long and short sentences were still a poetic noun.
Some dictionaries say that "long and short sentences" are "aliases of words". Or note "long and short sentences" as "irregular sentence poems". Not both of these notes are correct. After the Song Dynasty, it can be said that long and short sentences are aliases of words, but in the Northern Song Dynasty, long and short sentences are the real names of words. In the Tang Dynasty, long and short sentences were still a poetic noun. The so-called "long and short sentences" and "long and short" have their specific meanings and cannot be vaguely interpreted as "uneven length".
References:
Baidu encyclopedia-long and short sentences