The major elephant in the room here, which the memo doesn't seem to address, is that as late as the 1960's, computer programming was seen as a natural career for young women. Has biology changed that much in the last fifty years?
This is (also) a sexist stereotype, but maybe just maybe women are drawn to detailed work (say, needlepoint knitting, picking berries) while men are drawn to broad, imprecise work (such as selling insurance policies or chasing antelope). Maybe women are better at punching BCD numerical integrators for problems brought down from Feynman and Fermi, while men like coming up with a whole new language that compiles to PHP.
"Women" and "men" meant as generalities and not in the least implying that within-group variation can't be larger than between-groups variation.