2.1.20 [ISO32000-1] Section 10.6.3, Smoothness Tolerance
The specification states:
The smoothness tolerance (PDF 1.3) controls the quality of smooth shading (type 2 patterns and the sh operator) and thus indirectly controls the rendering performance. Smoothness is the allowable colour error between a shading approximated by piecewise linear interpolation and the true value of a (possibly nonlinear) shading function.
The smoothness tolerance is ignored.