the --owner option won't work?

[Mozo]

I want to sync the file ownership between two linux boxs. These two hosts
both have the same username, but the UID are not the same. For example
the UID of account "mozo" in source host is 500, and the target's is 505.

Refer to the rsync document, it says rsync will try to map to the target UID
by username. But rsync client with -a --owner --group options will set
the owner UID of the target file to 500. Did I miss anything?