Digital BW, The Print

As age begins to take over and I find myself pondering the question of life, I find it easier to ask completely absurd questions such as this one- What does a Black Only neutral curve really look like graphed in Excel? In theory if nothing else. In reality, I think it is impossible to achieve a truly compliant neutral curve because of the influence of the paper white and imperfections in the carbon inks.

However, as Lab L* progresses from 0 to 100, does Lab a* and Lab b* remain steady at 0? Wouldn't it require both a* AND b* to remain at the 0 axis to achieve a true neutral? A slippage of either a* or b* would induce warmth or coolness, yes?
 
If I were to graph this in Excel, Lab a* would be influenced by the paper color but would Lab b* remain on/near the 0 axis?

Phil