Sadly, the information in the OP is false.
Because Hiroshima data revealed the damaging effects of atomic bombs, the data itself was scrambled to the point that it nullified actual information and gave the appearance of little effect. People close to ground zero were blended with records of people far from grand zero and their original information detailing their exposure, captured in a code, was permanently deleted. Problem solved - now the atomic industry brags about the false data/comparisons. It’s creepy how methodical the nuke industry is...steadily erasing cold hard data and replacing it with worthless data. WHy would they go to such problems if the data did not reveal the problem?
In the following excerpt, the data for those exposed to the flash of the bombs was compared to the data for those not exposed - and there wasn’t much difference in mortality? The reason? Because both groups were equally harmed by the fallout so deaths from fallout related damage were comparable - and reported as “no effect from nuclear bomb”
“Here then was the confirmation of why the studies of the Hiroshima and Nagasaki survivors had not revealed any effects on their children. Everywhere in Japan, mortality rates had gone up due to the fallout, so that there was little or no difference between those survivors exposed to the direct flash and those who received the fallout in their diet over the years that followed.” Secret Fallout
Those in charge knew that the long term threats were not real. Otherwise the army would not have allowed our whole family to move to Japan 4 years after the bomb was dropped.
My father was stationed just 40 miles away from Hiroshima and our whole family lived there from 1949 to 1951. We visited Hiroshima and even met the mayor in the famous building shown so often representing what was left of the city. It was ground zero. Hundreds begged just outside that building and showed their burned skin and permanent wounds obtained during the war. I’m now 76 and cancer free. Brother is 80 no health issues. Mom lived to 95, Dad to 84 of natural causes.