RBR750 Local NAT Loopback Not Working

Did an experiment:

Connected RBR750 running firmware v7.2.6.31 to the primary Orbi network.  This router is assigned 192.168.1.71 to its WAN address.

Created port forwarding rules on the RBR750

• Port 5000 to LAN IP 10.0.0.2 (a Windows computer)
• Port 5001 to LAN IP 10.0.0.2 (the Windows computer)

Installed Rebex (free) web server on this Windows computer. Defined the listening ports as

• Port 5000 for http
• Port 5001 for https

Started the web server and told Windows to allow both private and public access through the firewall.

On the primary network, opened Edge web browser to https://192.168.1.71:5001 After the usual complaints about security, the Rebex web page opened.  Thus, the RBR750 forward connection from the WAN port to the internal web server.

Connected a Chromebook to the RBR750 WiFi network and opened Chrome browser to https://192.168.1.71:5001 (the WAN i.e. "public" IP of the RBR750).  After the usual security complaint, the Rebex web page opened.  Thus, NAT-loopback on the RBR750 sent the connection to the Rebex web server.

It would be a chore to set up a DNS entry to test this loopback issue and we've already seen that using the URL and the hardcoded IP address behave the same.

So, what is different?  I am testing against a plain vanilla web server and the goal is to connect to a Synology NAS, which I do not have to experiment with.

It is beginning to appear that the only consistent method of connecting with this Synology NAS is to use Synology Quick Connect.  Perhaps not the most efficient method in a network utilization sense, but consistent in both internet and LAN scenarios.