For example https://slightlyoff.github.io/ServiceWorker/spec/service_worker/#cache. If I want to actually open it at the right anchor, I need to select the URL in the location bar and press enter.

this currently redirects and thus it would require a new testcase. that said, doesn't look like something fixable in the location bar, maybe it's the docshell?

I'm fairly certain this used to happen because the old SW spec used a web components polyfill that added the content dynamically after the navigation. Now that the spec is using bikeshed this no longer triggers. WONTFIX'ing mostly because this is no longer reproducible since the conversion to bikeshed.