Eric Chaisson (the author of the web page mentioned in my prior post) at https://lweb.cfa.harvard.edu/~ejchaisson/cosmic_evolution/docs/fr_1/fr_1_part.html says the following.
"A Symmetry Argument Physicists are mainly charged with the application of the laws of Nature to the present state of something in order to predict its future. Although, in recent years, a renewed respect for the role of chance has somewhat diminished our ability to predict outcomes in the old, mechanistic, Newtonian sense, we still like to try our hand at predicting general trends, if not the details. In the case of the whole Universe, that “something” is literally all things—nothing in particular, just everything in general. Hence, if we find it hard to mentally reverse time to appreciate the earliest epoch of the Universe, we can instead take advantage of the natural symmetry of a model Universe that will eventually contract, and thereby predict the physical events destined to occur as a closed Universe nears its final phase of total collapse (see Figure 1.16). This procedure is valid only because the mathematics describing contraction are a mirror image of those for expansion. In other words, the events that will occur just prior to the end of a contracting Universe mimic those that already happened just after the start of an expanding Universe. Not that time ever does reverse, as best we know. Rather, we can use some of the symmetry built into the laws of physics to estimate the final events of such a hypothetically closed Universe, thus gaining some inkling of the initial events ~14 billion years ago. FIGURE
Even if the real Universe is not closed in this way and will never collapse to a singularity, astrophysicists employ closed models in order to understand theoretically some of the highlights of the earliest epoch of either a closed or an open evolutionary Universe. It’s an example of how we can use symmetry and scaling arguments—to scale models up, or scale them down, in this case to scale them back in time—in order to recreate mentally places and times we could never actually visit physically."