  Recently (Science, 355, 6320, 2017, 49-52) it was argued that density
functionals stray from the path towards exactness due to errors in densities
(\rho) of 14 atoms and ions computed with several recent functionals. However,
this conclusion rests on very compact \rho\ of highly charged 1s2 and 1s22s2
systems, the divergence is due to one particular group's recently developed
functionals, whereas other recent functionals perform well, and errors in \rho\
were not compared to actual energies E[\rho] of the same distinct, compact
systems, but to general errors for diverse systems. As argued here, a true path
can only be defined for E[\rho] and \rho\ for the same systems: By computing
errors in E[\rho], it is shown that different functionals show remarkably
linear error relationships between \rho\ and E[\rho] on well-defined but
different paths towards exactness, and the ranking in Science, 355, 6320, 2017,
49-52 breaks down. For example, M06-2X, said to perform poorly, performs very
well on the E,\rho\ paths defined here, and local (non-GGA) functionals rapidly
increase errors in E[\rho] due to the failure to describe dynamic correlation
of compact systems without the gradient. Finally, a measure of "exactness" is
given by the product of errors in E[\rho] and \rho; these relationships may be
more relevant focus points than a time line if one wants to estimate exactness
and develop new exact functionals.
