  In a previous work (Li et al. Science 364, 170) [1], we proposed a heat
transfer system that preserves the anti-parity-time (APT) symmetry, and observe
the rest-to-motion phase transition during the symmetry breaking. Recently, it
was suggested (Zhao et al. arXiv:1906.08431) [2] that the behaviours of the
system can be understood using scaling analysis based on the P\'eclet and
Nusselt numbers (Pe and Nu). It was further proposed that there exists a third
regime in the phase diagram in addition to the symmetric and symmetry broken
phases. Although we appreciate the proposal to characterize the contributions
of coupling, diffusion, and advection with dimensionless numbers, here we show
that they do not help to predict or interpret the behaviours of the APT system.
The dimensionless numbers do not provide enough details about the system to
conclude that there is a motionless phase, a phase transition, to find the
critical point, or to give the correct phase diagram with only two regimes.
