In the chapter titled "CHANGE IN THE NUMBER OF SWORDS PRODUCED" in The Yasukuni Swords, it is mentioned: "Nevertheless, Yasukuni smiths engaged in sword forging with maximum effort, always seeking to improve their techniques and produce the highest number of swords possible. They employed a sword forging method called 'makuri-gitae,' which is one of the relatively less time-consuming traditional methods, and it favored a hamon in suguha. This method seemed the most appropriate to the circumstances, and suited the forging of practical swords such as gunto."
It also mentions that "each smith produced about ten swords per month around 1935, and succeeded in increasing the monthly output to fifteen swords around 1940. Supplying for the Pacific War, which started on the 8th of December 1941, some of them surprisingly produced twenty swords per month in 1942, the year in which production reached its peak. It is speculated that this output was achieved by teams consisting of a swordsmith, two sakite, and a charcoal cutter, using no electric machines."
Given that traditional sword-making is a highly labor-intensive process, it indeed seems almost impossible to complete a blade in just two days without the use of power hammers or other modern machinery. This would require extreme efficiency and coordination from the entire team, pushing the boundaries of what could be done by hand in such a short time. Traditional methods, especially without the help of machines, would usually take longer, which is why the reported productivity is surprising.