This question has come up a few times, and hasn't gotten a large answer. I think this comment in Am I, a person living in the West, currently getting any thing out of of the medical experiments performed by the Third Reich and the Japanese Army during World War 2? written by u/churakaagii deep in a thread might be helpful. It also worth looking at the top level reply by u/commiespaceinvader that they mention, which while it exclusively talks about the Nazis, gets to the heart of the issue

You can read my discussion with /u/commiespaceinvader about Unit 731 here. I will start out by saying that I completely agree Nazi experiments were complete bullshit, and that even for Unit 731:

1. The vast majority of the experiments are not scientifically relevant
2. The vast majority of the tests were not performed with academic rigor
3. Of the rest that were scientifically relevant and conducted with academic rigor, most could have been and should have been done ethically.

However I have read Till Bärnighausen's article "Data generated in Japan’s biowarfare experiments on human victims in China, 1932–1945, and the ethics of using them" in Japan's Wartime Medical Atrocities published by Routeldge in 2010. I did link Bärnighausen's older research in my discussion linked above, and as Bärnighausen's conclusion has not changed, neither has mine. Yes Unit 731 was barbaric, what they did was deplorable, they should've been punished, and the vast majority of their research was complete junk. However, strictly on the realm of whether or not if there were results that were scientifically sound, valuable, and could not have been obtained otherwise, the answer is still, unfortunately, "yes".

Let me start by saying that Bärnighausen is of the personal opinion that all data gained from Unit 731 should be made public, because not all are and that is a big cause of the uncertainty regarding Unit 731, and an unconditional ban on their use should be put into place. This I do not disagree with. With that out of the way, Bärnighausen's research leads him to conclude that there are possibly experiment and data with results that were scientifically relevant, performed with academic rigor, and which could not have been done ethically.

Bärnighausen gives three examples:

Tuberculosis vaccination experiments

Dr. Futagi’s ethically reprehensible human experiments (as in all experiments of Unit 731, all human subjects were eventually killed) had an advantage over ethical experiments addressing the same questions in that they reduced the length of time needed to obtain meaningful results. From a practical perspective, ethical experiments were virtually impossible to complete, while Futagi’s experiments could be easily completed in a comparatively short period of time. In addition, the experiments enabled the researchers to derive results that were far more detailed and powerful than could have been obtained in ethical research, because the mode of infection and the exposure doses were controlled. The benefits to society derived from the results of the inhumane tuberculosis experiments might have been quite large, because the research was relevant to finding effective protection against a common, highly burdensome, and potentially deadly infectious disease.

Mustard gas experiments

The results of the mustard gas experiments were not only relevant for the design of offensive chemical weapons, but also for the treatment of victims of attacks with such weapons. Judging from the publicly available data, the experiments yielded meticulous descriptions of the clinical symptoms and laboratory parameters at frequent intervals after attacks with chemical weapons that had been carried out under controlled conditions. Obviously, such experiments can never be conducted ethically.

Frost bite experiments:

Starting in 1943, Dr. Yoshimura conducted cold experiments in a special laboratory building on the premises of Unit 731. The laboratory allowed the scientists to keep experimental conditions (such as temperature) constant and to conduct freezing experiments throughout the year (Cao 1951: 10–11; Han and Xin 1991: 116; Morimura 1985: 103). Despite the immense cruelty of the experiments, Yoshimura and his colleagues were able to publish some of their data in the English-language Japanese Journal of Physiology after presenting them at the 21st (in 1942), 22nd (in 1943), and 25th (in 1948) meeting of the Japanese Physiological Society (Yoshimura and Iida 1952a, 1952b, 1952c)....A number of later studies cite the three articles published by Yoshimura and colleagues in 1952 (Bridgman 1991; Hirai et al. 1968; Konda et al. 1981; Miura et al. 1977; Nelms and Soper 1962; Sawada et al. 2000; Spurr et al. 1955; Tanaka 1971a, 1971b). The authors of these articles and other medically trained readers would have realized that the experiments had caused the participants considerable pain....Some of the results of the experiments described in the three 1952 articles by Yoshimura and colleagues were relevant for medical practice. The reported effects of environmental factors (such as wind velocity or humidity) and individual factors (such as diet or sleep) on resistance to extreme cold could help to minimize cold-related injury. The experiments may also have been conducted reliably. The Japanese military scientists meticulously recorded the temperatures of each of the victims and controlled a large number of individual and environmental factors that are known to influence resistance to cold. Further, no research alternative existed for the experiments. In addition to the extreme pain experienced by the individuals forced to participate in the experiments, some of the victims suffered vasospasms that can completely block the blood supply to the affected body parts, causing necroses (Ulmer 1997: 721) – an unacceptable consequence in ethically conducted research.