When doing a simulation over a perfect system with biases, it is important to understand what it is the desired model.

If you apply a biases over such a system, it is no longer perfect, since the voltage drop introduces an asymmetry in the potential.

In a perfect system there is no natural place for the voltage drop to form and hence you get a slowed potential all the way through the scattering region,

which now will actually scatter electrons. This is of course correct if this is what you want to model is this.

If you want to model a perfect system with biases, you have to make infinite long when you apply the biases in order to avoid any scattering due to a potential slope,

but answer is in fact a much simpler one. The IV curve for a perfect system should always be calculated a zero biases calculation and then the IV curve should be calculated using linear response from the zero biases transmission spectrum. If you do this, it means that you would get the same results as in the literature.