I think another question worth asking is why the proportion of redshift has, to date, been only observable as a linear trend. Even the Hubble 30 year survey data revealed no hint at curvature in measurement yet many papers claiming it supports both increasing and decreasing expansion models have been released. On its face, they are illogical since neither has support from the data.
In comes dark matter which is essentially the mathematical band-aid for linear expansion. It is an unobservable force with the highly serendipitous effect of coincidentally keeping redshift effect since the origin of the universe observably flat.
Knowing that gravity waves propagate infinitely from their source, in the same manner and with the same power distribution as photons, we simply trend that dilational effect over time. You get a change in frequency of all photons traveling in that space over time, a completely linear trend, and in a spacetime manifold model one can still claim that there is expansion of space albeit at a very slow and non-accelerating rate. It is compatible with all observed effects in the universe of which I am aware, and does not require anything that is not lab proven 100 year old theory.
I dislike appearing to be a broken record, but I have yet to find this Dilation Flooding theory duplicated anywhere in science. I post challenges to other theories not to be combative but in honest consideration of where they don't seem to match observations in my search for what is more true.
My hope is to find earnest consideration or merit-based challenge to see how true this theory is. To be proven wrong would be better than no engagement at all.