Basically everyone at Harvey Mudd is in STEM -- the article says this. Their results are not really useful in the discussion, as their female student population is already heavily self-selected in favor of the hard sciences.
Adding on to this, Harvey Mudd puts forth significant effort at outreach and recruitment for their student body. Meaning they're pulling from the existing pool of STEM students to a large degree compared to creating new ones. It's very likely that Harvey Mudd's success cannot be reproduced at scale.