My guess would be that they did not field formations that warrants it. But the designers can probably tell us more...
A two minute Google search yields from:
https://history.army.mil/books/korea/ebb/ch3.htm:
"The units committed included the best in the
People's Liberation Army. The
Fourth Field Army, commanded by Lin Piao, was the strongest, and its
XIII Army Group included armies honored for past achievements with the title of "iron" troops.17 The
Third Field Army, commanded by Chen Yi, was not particularly strong as a whole, but its
IX Army Group included at least one army considered to be a crack unit. But however highly rated by
People's Liberation Army standards, the two groups essentially constituted a mass of infantry with little artillery support, no armor or air support, and primitive, haphazard logistical support. They were, characteristically, poorly equipped. Individual and crew-served weapons, from company to army, were a collection of diverse makes and calibers; other equipment was equally mixed; and both weapons and equipment were in short supply, small arms to such a degree that as many as two-thirds of some infantry units lacked them. Their strongest points were experience and morale. Most of the troops were veterans of the recent civil war, and virtually all senior officers had fought the Japanese during World War II. Their high morale presumably was the result of effective political indoctrination, notwithstanding that former Nationalist Army members constituted much of the strength of the intervention force. It was on a combination of morale and guerrilla warfare tactics that Chinese leaders had long depended to compensate for inferiority in weapons and equipment. Supporting the efficacy of this "man-over-weapons" doctrine were successes against the Japanese and Nationalist Chinese, and most recently against the United Nations Command.18"
17 Officers of the
People's Liberation Army were not designated by nominal ranks as in the U.S. Army. Troop commanders held positional ranks and staff officers held equivalent ranks. The commander of a regiment, for example, held the positional rank of regimental commander, and a regimental staff officer held the equivalent rank of assistant regimental commander. See DA Pam 3051,
Handbook on the Chinese Communist Army, Sep 52, pp. 75-76.
18 Alexander L. George,
The Chinese Communist Army in Action (New York: Columbia University Press, 1967), pp. vii-viii, 5-7, 83-84, 173; Samuel B. Griffith II,
The Chinese People's Liberation Army (New York: McGrawHill Book Company, 1967), p. 131; Gittings,
The Role of the Chinese Army, p. 77; DA Pam 30-51,
Handbook on the Chinese Communist Army, 7 Dec 60, pp. 8, 66; ibid., Sep 52, pp. 38-39; GHQ, FEC, Order of Battle Information, Chinese Communist Regular Ground Forces (China, Manchuria, and Korea), 9 Dec 51.
Small world...just ordered a copy of 18 yesterday.
I'm sure that Andy and others will shed more light on these design choices.
Bill