Does someone know how the Minoston MT10W works?

I just got some Minoston MT10W count down timer switches for fans in bathrooms. They have wifi capability and I have them working with the Minoston app. But I’m confused as to how exactly they work (and repeated questions to Minoston hasn’t cleared it up for me). I wanted to normally only control them on my local wifi network. I was told that the app communicates with someplace in the cloud and that communicates back to the device. I’m not sure if that is just for configuration or for normal operation of the switch from the phone. So I didn’t want to allow internet access to the device. They suggested blocking it by my router firewall using the MAC address of the device. My firewall only blocks by IP or geographic region and not by MAC address. But then I found a place in the router that let me block traffic by device MAC address (thanks to Copilot). So I did that.

The app properly complains that it doesn’t have network connection and all the devices (3) are “offline”. That sounds great. But if I tried to access one of the devices, I got a prompt to allow the app to turn on the Bluetooth. I did that. I retried the device and after another prompt complaining and suggesting going back to the “homepage”. I returned to the list of devices and after a few seconds, all of them went online. I could control all of them from the phone.

So does someone know if these devices are “dual mode”? I THINK I have it configured now so that internet can not get access, and Bluetooth allows connecting to the devices from the app. But maybe they are tunneling back through again somehow that the router isn’t blocking.

Also I was a little surprised that, if it IS using the Bluetooth connection, it was able to communicate from my master bedroom all the way across the house and up a floor and through several walls. I didn’t realize Bluetooth had such a range. (I looked it up and it said 300+ feet, but I thought walls and the like would shorten that).

So has someone else investigated how these devices work?