Question about port forwarding

I'm trying to understand how OpenSense works with port forwarding.

I opened a port (25565) for my Minecraft server and it's not working when I try accessing it using <public ip>:25565 while on a local LAN network. However, I am able to join by using the <server ip>:25565 via LAN.

When I'm connected via a mobile hotspot, accessing it with <public ip>:25565 works perfectly. Why won't it work correctly from within my local LAN? I'd like to test the external IP from within the LAN in case external access gets lost.