I don't think the claim that they would not have broken anything can be backed by facts.

If you look at Microsoft, for instance, their programmers used to write very buggy code, but with the introduction of better processes, like their Secure Development Lifecycle, they saw a substantial improvement in code quality (as measured through security and reliability metrics).

The damage done by not following a quality assurance process and writing buggy code was so big that Microsoft's image will be affected for a long time, even though they have now improved the code quality.