  The point-splitting renormalization method offers a prescription to calculate
finite expectation values of quadratic operators constructed from quantum
fields in a general curved spacetime. It has been recently shown by Levi and
Ori that when the background metric possesses an isometry, like stationary or
spherically symmetric black holes, the method can be upgraded into a pragmatic
procedure of renormalization that produces efficient numerical calculations. In
this note we show that when the background enjoys three-dimensional spatial
symmetries, like homogeneous expanding universes, the above pragmatic
regularization technique reduces to the well established adiabatic
regularization method.
