The key to understanding the difference between Historical Science and Operational Science is observation. Since we live in the present, we can only observe the present. Because we do not live in the past it is impossible to observe the past. As a result the past can only be studied by observing in the present. This means that to study the past requires making some assumptions about the past. Since by definition the study of origins is by definition an Historical Science, it highly influenced by philosophical assumptions. And if those philosophical assumptions are wrong then so are the conclusions.
Operational Science on the other hand while not totally free of philosophical assumptions because it occurs in the present those philosophical assumptions have less of an influence. It is operation science that has produced the technological wanders we have today.