This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the American Institute of Physics. ; In a previous article [J. Chem. Phys. 138, 084108 (2013)], we showed that the transition-state-theory (t ? 0_+) limit of ring-polymer molecular dynamics rate-theory (RPMD-TST) is also the t ? 0_+ limit of a new type of quantum ux-side time-correlation function, in which the dividing surfaces are invariant to imaginary-time translation; in other words, that RPMD-TST is a t ? 0_+ quantum transition-state theory (QTST). Recently, Jang and Voth [J. Chem. Phys. 144, 084110 (2016)] rederived this quantum t ? 0_+ limit, and claimed that it gives instead the centroid-density approximation. Here we show that the t ? 0_+ limit derived by Jang and Voth is in fact RPMD-TST. ; We acknowledge funding from the UK Science and Engineering Research Council. TJHH also acknowledges a Research Fellowship from Jesus College, Cambridge.