ServletContex is not JSP 2.5 compilant

in the jsp the

<%= application.getServerInfo() %>

return jetty-6.1.11
that seem not 2.5 specification compilant http://java.sun.com/products/servlet/2.5/docs/servlet-2_5-mr2/index.html.
The ServletContext.getServerInfo() apidoc interface tell "The form of the returned string is servername/versionnumber"
I expected jetty/6.1.11 instead.

For example:
tomcat 6 return Apache Tomcat/6.0.16
or websphere 6 return IBM WebSphere Application Server/6.0