Well you’re partly right, yes it biases the mip selection but mip selection is not based on distance but rather the texture resolution and how quickly the texture coordinates are changing.
Typically, using a negative bias will introduce aliasing as it is trying to select a higher resolution mip than is appropriate for the view.
In your case, if setting the bias to 0 doesn’t resolve it then I’m not sure what the issue could be, as your geometry looks too simple to be introducing any aliasing of its own.