[leafnode-list] When is usexhdr useful in leafnode 2?

[Adam Funk]

The man page for leafnode 2 says:

  usexhdr = 1
    fetchnews will usually use XOVER to retrieve header information
    from the remote server.  Under special circumstances, it may be
    faster to have it use XHDR instead.  This line will try to enforce
    XHDR, but fetchnews will still fall back to XOVER if you also want
    to use filters in a group or if you work with "delaybody" set
    (because in these cases it will always be faster to use XOVER).

What are the mysterious "special circumstances"?

I've just noticed the "config: usexhdr does not work together with
filtering or delaybody mode" warning in my logs; my config file has
"usexhdr = 1" under nntp.aioe.org, but not in any of the other
upstream server configs, & I can't recall when or why I put it there!

Thanks,
Adam