In Bangladesh there was a Internet blackout recently, so if we use Internet despite the fact that it can go also puff , what's wrong with another similar service?
You missed the part where the service is using GSM to relay the transaction.
If the government can cut internet they can order mobile providers to cut GSM coverage too, besides, your node would still need internet to broadcast your tx to the chain, so you will either need someone with internet in the country or someone who can still make international calls, and in case of a coup that is not a solution.
Let's not even think of the other fact, who actually uses SUI?