Looked into liquid, there are 15 functionaries that have the power to peg out L-btc to btc, 11 of the 15 must agree to sign the transaction that allows btc to peg out. So while you are correct it is more then just block stream, if any 5 of the 15 functionaries were to go down, no bitcoin could be removed from the network. Also, the actual functionaries seem to be obfuscated by the overall membership numbers, so for some reason they aren’t very transparent with who actually has the control over the network.