X-Query-Routing 0.1 only?

Looking though the code it seems like (big maybe) this will only respond to clients that have X-Query-Routing 0.1 in the connect header and (or??) must have a ultrapeer false header.
So what about no header? What about 0.2 ? if there is even a version 0.2 now, but what about later on?
And what does it matter? if you route packets better than a old client, no need to tell everyone, just do it.
Plus, what does this have to do with ultrapeers, is X-Query-Routing required to connect to a ultrapeer?
just wondering if it's a bug that was overlooked or what.

CString RoutingHeader = FindHeader("X-Query-Routing");
if(!RoutingHeader.IsEmpty() && RoutingHeader == "0.1")
QueryRouting = true;