copy tag shows repo revision, not tag revision - why?

When copying a tag (URL -> URL), the log message shows the repo
revision at the time of the copy, rather than the last commit revision
of the tag.

This occurs if no revision is specified, or if the revision is
specified as HEAD.

The only way to get the log message to show the last commit revision
of the tag seems to be to specify it on the svn copy command; this is
tedious and error-prone.

Is there any simpler way to ensure that the log message shows the last
committed version of the source tag?

This is with svn client
svn, version 1.6.16 (r1073529)
Received on 2011-09-10 22:10:29 CEST