Works for me.

Set up the Client to lock to the AP's SSID (WiFi survey -> select AP -> click Lock to AP -> Apply -> Save).

Disable ESSID broadcast on the AP, apply, save.

The client CPE will disconnect from the AP (as it does if any WiFi settings are being changed).

Wait for the client to re-connect (may need up to 10 minutes).

Client eventually re-connects to the AP.

Do a WiFi survey on the client to check for ESSID -> it's gone, but the AP still being recognized (the BSSID or MAC address and its name still appear in survey).