Xiaomi Gateway : Will it work after disabling internet access?

I’ve used my router to block internet access to the Xiaomi hub and immediately in the Xiaomi phone app I can see that it’s gone offline.

I can still see my temp sensors updating in OpenHAB which is great…
I can also see the ambient light sensor in the hub is reporting it’s levels to OpenHAB…

However I don’t seem to be able to control the LED in the hub any more… Is this just how it is or is something wrong?

I block Internet for the hub and don’t have any issues. I don’t try change the hub led so not sure if it’s a problem.
I don’t use the phone app at all (uninstalled)

Same here.

Still works fine.

Without the app and with blocked access to the gateway, can you add new devices to the gateway (I’ve just bought some Xiaomi gear).