featureis being rebased onto
master, the first re-applied commit will break your build, but as long as there are no merge conflicts, the rebase process will continue uninterrupted. The error from the first commit will remain present in all subsequent commits, resulting in a chain of broken commits.
He specifically mentions the problem here. He’s not saying that the problem is the error existing in the first place, this would happen whether you rebased or merged. What he’s saying is that the error will be present in every commit. If you merge however, it will be that single commit that introduced the error and it’s easily tracked and fixed.