Thank you very much for the clarification.
However I think this needs some official documentation.
Also it is unclear why this only covers the "App Limits" section of Screen Time and not the very similar content-based restrictions. In both cases the limits are based on the URLs of web sites, so there's no logical difference.
If you expose these errors to Apps, they really needs to be documented and "stable". Apps need to know the reason for errors in order to be able to respond correctly.