  We consider the diffusion constant, D, of a probe particle coupled to the
East model, extending previous numerical results for this model to encompass a
total of twelve orders of magnitude in relaxation time, {\tau}. Our
considerations thus cover the full range of relaxation times relevant to
experimental studies of reversible glass formers. Throughout this range, we
show that the results of the model are consistent with a fractional
Stokes-Einstein law, D \propto {\tau}^{-{\xi}} with {\xi} \approx 0.77. The
same data can also be fit by relating D{\tau} to the East model excitation
concentration q, specifically, D{\tau} \sim 1/q^{\alpha} with {\alpha} \approx
1.6. In either case, breakdown of the Stokes-Einstein relation in this
kinetically constrained model is unquestionable and large.
