As far as we know, yes.

On one hand, a good deal of evidence and descriptions of the plan came from members of Japanese biological warfare units such as Unit 731 during the Khabarovsk War Crime Trials of 1949. Scientists who had worked for BW units confessed at length the things they had done and planned to do, including Operation Cherry Blossom.

On the other hand, trials conducted by the Soviets were sometimes known for forced and falsified confessions. However, Operation Cherry Blossom was absolutely in line with other crimes of Unit 731 and their colleagues. Most historians agree that the Japanese War Crimes trials were based on facts, because the extent of their crimes were such that the Soviets didn't need to make things up. Additionally, it seems that the Soviet wanted information gathered by the Japanese, so it would've been in their interest to not falsify information.

In short, while it is possible that Japanese scientists were either coerced into a false confession by Soviet authorities or created a fake plan to give the Soviets what they wanted, in hopes of a lighter sentence, it seems unlikely. Operation Cherry Blossom was in line with the kind of things Japanese forces committed and planned to commit.