The web views the filters don't apply to have different use-cases such as customizing/hiding the browser UI elements, injecting Javascript, etc. There are legitimate reasons to use it in some cases (in case you need to display server-side-rendered content as if it was native).

Of course, Apple could decide on a case-by-case basis and reject usages of the legacy web view when the new implementation is appropriate, but they won't just like they don't do anything for apps that lie on the "privacy nutrition labels" about the data they collect or various other breaches of the App Store guidelines.