They are mixing apples and oranges, XC is trustless based on the signatures of all parties during the private transaction.  Its not using MULTI_SIG N OF M Address's.

The transactions are SIGNED BY ALL PARTIES, if any of the outputs are missing, then it is not signed by all parties.



Here is an example of a private decentralized distributed multi-path transaction consisting of 4 parties. >>> http://chainz.cryptoid.info/xc/tx.dws?229236.htm