[NNTP] References Command

Is there a simple way to return a list of articles referencing a certain
article?

Currently, when I receive an article number, and want to fetch the articles
referencing it, I have to do a full XOVER on all groups that may possibly
contain a reply to that article. It's very inefficient, but it seems the
only way. The only alternative would be: 'XPAT References <msgid>', but a
very large percentage of the newsservers don't support XPAT because it uses
too much CPU. If there was a command like 'REFERENCES <msgid>', servers
could implement it much more efficiently than XPAT, since wildcards (*)
aren't allowed, so all it needs is a single hash-table.

Is there a specific reason why such a command doesn't exist? Or is it very
unusual for replies to be posted to a different group than the original
article?