Since most of the smurfs Are on With the same Wifi and Same PC, Then the Riot system on matching the existing account having the same mac address and the public ip address and match the player with the rank they belong
Drawback :-
- Player who is playing on the same client like the two brother or something sharing the same pc mac address/wifi could result in wrong match making.
- Public IP address could be bypassed by Using a vpn
Conclusion :-
It will be better that Riot mm system put more imphases on IP Address and Mac address