The physical basis of GR/spacetime, is that in a moving frame any activity is slowed, because the combination of the speed of the frame and any activity within it cannot exceed the speed of light.
Remember that at the speed of light, time supposedly stops. That's because there can't be any additional motion that could be measured in a frame moving at the speed of light.
Which then goes back to the issues you mentioned in the Hubris of Western philosophy, as expressed in mathematics. The assumption that math is foundational to the reality, rather than an abstraction from it. That the map is foundational to the territory.
Because then they took this idea that space "shrinks," rather than the metrics derived from a moving frame shrink, and turned it around to say that space expands.
Consider that if we take the original concept of a moving frame, remembering that in a frame moving at the speed of light, time stops and distance shrinks to zero, then consider that the frame with the longest ruler and fastest clock must be the one closest to the total equilibrium of space. The unmoving void of absolute zero.
So then the real qualities of space, the conceptual parameters, are not so much three dimensions, which are a mapping device, like longitude, latitude and altitude, but equilibrium and infinity. Like the number line, from zero to infinity.
The light radiates toward infinity, as structure coalesces toward equilibrium.
The problem was that it was originally assumed that cosmic redshift was basic doppler effect. Then they came to see that it increases proportional to distance in all directions. Which either meant we are at the exact center of the universe, or that redshift must be some optical effect. Yet the only known cause would be some medium interfering with he speed of the light, aka, tired light theory. Though there didn't seem to be any other distorting effects of this medium, so than it was argued space itself must expand, based on the math built to explain Relativity. That if it can shrink, it can also expand. Ignoring the underlaying factor that the speed of light remains constant, whatever the frame is doing. So that if it expanded, the speed should increase, in order to remain constant.
If you look through any descriptions of this universal expansion, like the one I posted, they all use light speed as the metric to gauge this expansion.
Yet keep in mind, the primary proof of this expansion is the redshifted spectrum of the very same light, that is crossing this space. So try adding up the logic of arguing we know space is expanding, based on the spectrum of this light, but the speed of the light crossing it is some other metric we just have laying around, to gauge it by.
There is a way light does redshift over distance, as multi spectrum packets, as the higher frequencies dissipate faster. Yet that would mean we are sampling a wave front and the quantification of light is an artifact of its interaction with the physical devices used to absorb and measure it. A loading, or threshold theory.
Yet given the entire foundations of modern physics are based on measurement, then these quanta of light must be foundational and we must be detecting photons of single spectrum light that crossed billions of lightyears.
An interesting interview, from some decades ago;
https://worrydream.com/refs/Mead_2001_-_Interview_(American_Spectator).html
