I don't read this as saying they'll prevent further breaches. It seems to be saying that they will improve compliance with data privacy regulation.
We're so used to the only kind of data protection enforcement being for data leakage - but this is actually a great example of what GDPR is really for: putting a framework around what personal data it's acceptable for companies to process in the first place.
One of the ways in which a business can harm you through abusing the data they have about you is certainly allowing it to leak out - but that is very much not the only intention of data protection law.