1451 is the date the hwacha is supposed to have been invented in Korea. Was there a precursor with a similar configuration in the Ming dynasty prior to 1451 that is not like the earlier huoche version?
I have no idea regarding the construction of the huoche used Jingnan war (1401-1403). But jugding by the "Wubei zhi" image we can assume that Mao Yuan Yi just copied this pic from Wujing Zongyao (ashe used samples from more than 2000 old treatises). IMHO the answer is in original edition of Wujing Zongyao.
Let me quote the article from Korea (by Yang Sung-jin) regarding hwacha.
On Jan. 16, 1451, King Munjong appeared in a military exercise taking
place near the palace. A total of 700 soldiers formed a tactical lineup
composed of a mock attack and defense. The operation was orderly and fine-tuned, the Annals historiographers observed.
Meanwhile, cannons were test-fired in front of the king. Then, the soldiers performed a demonstration of hwacha (fire cartwheel) which shot through all the targets positioned 80 steps apart.
So there is no indications that the weapon was invented that time, but only the demo-firing of this weapon was mentioned.