As someone who has followed the subject since the 70's, I'm not entirely convinced the model is as coherent as it's claimed to be.

Usually when observation doesn't match prediction, it is assumed the theory is falsified, rather than it just needs another patch.

Before Inflation, Dark Matter and Dark Energy, the original patch was when they realized that as cosmic redshift increases proportional to distance in all directions, it makes us appear to be at the center of the universe. So it was changed from an expansion in space, to an expansion of space, because "spacetime."

Which totally ignores the central axiom of Special Relativity, that the speed of light is measured as a constant in all frames. If intergalactic light is being redshifted, obviously it is not constant to intergalactic space. More lightyears, not expanded lightyears.

In this model, light is treated as a wavy line, that as it is stretched, becomes less wavy. Which ignores that waves are generated by the energy traveling.

In classic doppler shift, as the source recedes, each wave takes a little longer to cross, so it is measured as a lower frequency. Yet this still requires a stable metric of space and it is distance in this space that increases. The train moving away doesn't stretch the train tracks. So two metrics of space are being derived from the same light. One based on the speed and one based on the spectrum.

Now this theory is still treating the speed as the denominator, since it would be a "tired light" theory, if the speed were the numerator. So it hasn't escaped from being classic doppler effect.

Consequently we are either at the center of the universe, or there is some unexplained optical effect causing cosmic redshift, as we are at the center of our point of view.

Here is an interesting paper I came across years ago;

2008CChristov_WaveMotion_45_154_EvolutionWavePackets

Pointing out that while single spectrum light will only redshift due to recession, multispectrum light "packets" will shift over distance, as the higher frequencies dissipate faster.

The rather large Pandora's Box this opens, is that means we are sampling a wave front, not individual photons travelling billions of years, meaning quantization of light is not fundamental, but a function of absorption and measurement. So each quanta of light, aka photon, would include an increasingly broader spectrum the further the source is, so the redshift increases proportional to distance.

As this effect compounds, it explains the parabolic curve in the rate, currently explained by Dark Energy.

Safe to say, this is outside approved discussion, so file it under crackpottery.

Multiverses are much more tolerated.