The gdpr plugin let you delete username at more places. Also from the changelogs as used by the authorstat plugin (if I saw correctly at the first glance).
However, I do not know if the authors regenerate data regularly, or that it more robust to have a reset of some stuff first maybe. In that case I have also not yet idea what exactly and if it could have side effects. For these details better ask in issue tracker the author of authorstats plugin.