That's by design, we only reset the metadata of the revision.
repository sync <repos> [rev]
Resume synchronization of repositories
It works like `resync`, except that it doesn't clear the already
synchronized changesets, so it's a better way to resume an interrupted
`resync`.
See `resync` help for detailed usage.
(as you can see, the inline doc is incomplete…)
This was implemented in order to support the post-revprop hook in Subversion (#6016).
The only reason I could see to resync completely a single svn change would be in case the actual file changes changed… did they implement svnadmin backout? ;-)
