Placeholder replication level does not seem to be working

Steps to reproduce

1. Configure Replication App on 2 instances (I've reproduced this on 2 local XWiki 17.10.7 Jetty/HSQL instances running on different browsers and different ports)
2. On instance A, create a page (e.g. 'ReplicationPlaceholder')
3. On this page, go to Administer Page > Other > Replication
4. From 'Page and children' section, select 'All instances', Replication level: Placeholder
5. Click 'Save' button
6. On instance B, refresh the browser and observe the Navigation Panel

Expected results

On the instance B, the page was replicated (containing the warning that the page is just a placeholder for a page which exists on another replication instance).

Actual results

The page is not replicated on instance B.

On instance A (the owner  of the created page, e.g. 'ReplicationPlaceholder'), on Replication tab, the Replication level is displayed as 'Everything', but it should be 'Placeholder'.