Author here: I did send it send the device for repair repeatedly like 4 times until the warranty ended and the company charged me huge. So decided to spend time on it. I am usually interested in knowing how my devices work so I couldn't resist. Leaving a bricked device at home was one option, learn from it was another, so I picked the second.
Does it really? In my opinion, if it stops working and it's under warranty, why not send it out for repair? They did no changes to the actual device, and apparently it was working fine for a few days without network connection, so if it suddenly stops working and it's under warranty that's the manufacturer's/store's problem, not theirs. Trying to fix it/reverse engineer it takes time, and I can see someone with these kinds of skills wanting to spend it on something else than trying to figure out how the manufacturer bricked their vacuum.
In addition, _someone_ is paying for the repairs under warranty, so if enough people were to do it, hopefully it would disincentivize completely blocking devices just because they can't reach a server.