The type definition for the checkIgnore configuration option is misleading as it tells developers that args is an array of LogArgument. We've found that actually what you're getting is a Javascript arguments object.
This means that although you can index into it, many array functions are not actually available to you on this object. The annotation should probably be updated to be iArguments.
This caused an issue for us where we were attempting to filter out specific errors by looping over args looking for ignored instances. Correct typing probably would have indicated earlier that this was not going to work.