Since the arguments are bitfields of which player to ban or not it can only store info of up to 32 players in one argument, so the second argument is for the other players, if the server has more than 32 slots.
See the code
here.
Here's more info about the VoiceMask user message, which contains this info as well as info about which other players the player is able to hear (e.g. teammates). The usermessage sent by the server might be more reliable against players spaming shit ;)
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