If you don't see the article's link to the research - https://www.pnas.org/doi/10.1073/pnas.2610287123 (yes, paywalled):
"Sugar rationing" is far too simplistic a description of the historical situation: https://en.wikipedia.org/wiki/Rationing_in_the_United_Kingdo...
Yeah the article doesn't mention how they account for all the other changes in people's diet, stress, environment and what not that happens during and after a war...
Plus, you might want to go back a year pre-conception, at least on the father's side. Sperm cell production is a fairly long process, definitely emphasizing quantity over quality, and thus easy for all sorts of environmental factors to affect - https://en.wikipedia.org/wiki/Spermatogenesis#Duration through https://en.wikipedia.org/wiki/Spermatogenesis#Influencing_fa...
I became immediately suspicious due to how complex the rationing schemes were.
Even the labels put on food like "margarine" aren't composed of what you'd normally expect, as they shifted to fish/whale oils due to availability.