Redirects of an included file re-route the whole page to the new location

I tried the script where one of the included pages contained a redirect to a new page. My expectation was that the html-content of the redirection would show up in the document. What I observed was that the whole page (containing the inclusion) was redirected to the the new page. I'm not sure if this is in the scope of the project so feel free to close this issue if it's not.