Yield protection means a college will defer some/many applicants that they think will be accepted and enroll elsewhere. It does not mean they will defer all such cases, because they do want to fill their classes with many of these kids.
Many colleges these days (not sure about GaTech, but Tulane and Northeastern are examples) use sophisticated data analytics to predict who is likely to enroll and who is not. They take into account not just stats but where they are applying from, what their SES status is, historical enrollment track record of their high school, etc. So yield protection isn’t driven purely by GPA and test scores.