Otherwise it is not. It appears that the replication filter is evaluated
using the access rights of the user making the modification, not those
of the replication user.
IIRC, the syncrepl client should connect to the provider, bind as the
identity configured on the syncrepl client, then perform a search with the
filter configured on the syncrepl client.
As such, the "user making the modification" should never enter into the
algorithm. You should be able to verify this with "slapd -d access" on the
provider. Give it a try and see if it looks sane, i.e. you should only see
references to the identity configured on the syncrepl client in the course
of a syncrepl connection.