We are stretching the metaphor thin, but surely the progress towards an atomic bomb was not measured only in uranium production, in the same way that the progress towards a QC is not measured only in construction time of the machine.
At the theory level, there were only theories, then a few breakthroughs, then some linear production time, then a big boom.
> Something doesn't add up here.
Please consider it might be your (and my) lack of expertise in the specific sub-field. (I do realize I am saying this on Hacker News.)
Not only, but a huge challenge was manufacturing enough fuel and was the real limiting part. They were working out hard science and engineering but more fuel definitely == bigger bomb in a very real way and it is quite linear because E=mc^2. And it was in many ways the bottleneck for the bombs - it literally guided how big they made the first bomb and the US manufactured enough for 3 - 1 test, 2 to drop