In other words it takes a certain level of physical ability to perform the job safely, period. Therefore the physical fitness requirement should be the same no-matter who is applying.
Guess what, men and women are different. In general there are differences in size and physical strength between men and women. That's not a gender bias, it is a well documented and studied trait of our species. (our species is not alone in this either, it is quite common) No amount of liberal hand-wringing and wishing we were all truly equal in some unicorn dotted landscape will change that basic fact.
Apparently the physical requirements are not particularly stressing as what, 94% of men who apply pass the test? Ok, it is likely that only people reasonably fit even apply, but that is still an extremely high pass rate. Apparently 71% of women who apply pass too. That is also a great pass rate. It tells me that passing the test is not impossible for women, and in fact nearly 3 out of 4 women who try it do pass.
Due to the respective bell curves for physical ability, if you made the physical test hard enough that only 50% of men passed it, then essentially NO women would pass.