To me, it doesn't add up.

Redshift implies a stable metric. When the train moves away, it doesn't stretch the train tracks.

Similarly, the speed of light remains the metric against which this expansion is measured. There are more lightyears, not expanded lightyears.

The premise of spacetime is that the speed of light remains constant to the frame, but if intergalactic light is redshifted, it's not constant to intergalactic space.

It goes back to when they first realized that as this redshift is proportional to distance in all directions, it makes us appear to be the center of the expansion, so it was changed from an expansion in space, to an expansion of space, because spacetime!

Yet how can that be, if it violates the basis of spacetime?

Multispectrum light "packets" do redshift over distance, as the higher frequencies dissipate faster, but that would mean we are sampling a wave front, not observing individual photons having traveled billions of lightyears. Which goes to the fundamental quantization of energy....

If this is an optical effect, compounding on itself, that would explain the curvature of the rate of redshift.

The background radiation would be the light of ever further sources shifted off the visible spectrum and I suspect the James Webb will find this radiation to be a bit more complex, than that of an initial effect.

I could expand on the idea, but the groupthink on this topic is pretty strong, so I'm just waiting on the James Webb.