Well, sure. Put another way: discrimination is highest in professions where a group is discriminated against the most, and ignoring the strongest sources makes the overall effect weaker. Not big surprises. Do we want to do that though?
The study says nothing about the underlying reasons for that discrimination though. The point of discounting those two roles in my post was to test my personal hypothesis of the underlying cause based on the data at hand - not to trivialise the findings of the authors.