You were trying to use the string "Network Login MAC user". In the "Network Login MAC user", only "MAC" is the string parameter (%0%) you can use in log filter and others "Network Login user" is not string parameter.
So that is the reason why your log filter didn't work
Therefore, if you want to use match condition with "string" parameter, you should use one of "string" parameters in the log (there are three string parameters in the log, %0%, %1% and %5%).
For example with your way, I think you can use %0% string (i.e. "MAC") as below: configure log filter "DefaultFilter" add exclude events "nl.ClientAuthenticated" match string "MAC"Otherwise, you can also use other match condition, "mac-address", "ports" or "vlan" instead of "string" parameter.