It's easier to do it over the internet with all the HTTP-oriented infrastructure we have nowadays. If I were the developer and just want it done quickly and reliably, I'd do a central server thingy as well.
So that when the manufacturer goes out of business (or decides that continued support isn’t profitable) it becomes a paperweight.
I'd be fairly confident that Weber will be in business selling grills 5 years from now. Still supporting some little Bluetooth gadget experiment, on the other hand...
This isn't IoT, it's bluetooth, and works fine without an internet connection.