Request.Unvalidated("") doesn't work as advertised

I have this in my web.config:
<httpRuntime targetFramework="4.5.1" requestValidationMode="4.5" /> I am navigating to this page: http://site/page.aspx?Text=<tag>bla,bla</tag>
I would like to prevent validation on this query parameter so from code behind I get the value like this:
Dim s as String = Request.Unvalidated.QueryString("Test") Acording to the documentation I should not be getting this error:
A potentially dangerous Request.RawUrl value was detected from the client (="...Text=<tag>bla,bla</tag>").
I am running in classic mode not integrated if that makes a difference.
I get this error even when using  ValidateRequest="false" page directive although I would rather be ...