Doesn't everyone studying for a bachelor's degree in applied physics have to work out things like critical mass and how to avoid premature explosion?

At least we did when I was studying for my Applied Physics degree in the mid 70s. It was not regarded as even slightly controversial that we should do so nor that it was especially difficult. It was simply one of the problems set in the nuclear physics course.

Of course we didn't go into the same degree of detail as Dobson, Pipkorn, and Selden and our solutions would probably not have been as effective but that was mostly because it was the thought process rather than the ultimate result that was important.