There is an excellent Q&A about why diesel engines have lower redline RPMs (about 4500 RPM) than gasoline engines (about 6500 RPM). The reason is related to the combustion of diesel fuel.
However, what would happen if you manage to over-rev a diesel engine to, say, 5500 RPM by downshifting a manual transmission on a freeway? Surely, the engine management system would detect an over-RPM condition and would stop diesel fuel injection. Then there is no combustion happening, and the reason for diesel engines having a lower redline does not seem valid anymore.
My understanding of gasoline engines is that they generally break when managing to over-rev them. Does a diesel engine break when running at 5500 RPM? If so, why does this happen if gasoline engines can take 6500 RPM and if diesel engines are generally more sturdy than gasoline engines?