DefaultGetServlet errors during any bundle install
On a fresh AEM 6.5 SP4. Whenever I install either a new AEM archetype project or the WKND starter project, AEM (or Sightly most likely) seem to unregister, and only come back once the OSGi Bundle is fully Active. Is a brief 4-10 seconds outage I get the image below

There is also a long stack trace but this is what it says
02.06.2020 01:09:53.093 *ERROR* [172.19.0.1 [1591060190870] GET /sites.html/content HTTP/1.1] org.apache.sling.servlets.resolver.internal.SlingServletResolver Original error null
02.06.2020 01:09:53.095 *ERROR* [172.19.0.1 [1591060190870] GET /sites.html/content HTTP/1.1] org.apache.sling.engine.impl.DefaultErrorHandler Error handler failed:java.io.IOException
java.io.IOException: Error handler failed: org.apache.sling.api.scripting.ScriptEvaluationException
We would understand our own pages to be down during deployment, but we do not understand why the rest of the platform (likes sites.html or assets.html) have to go down. Is this the expected behaviour?