I think that almost all gravity speculation has two fundamental flaws, and your question is beautiful because it exposes these flaws in a manner that directly address them.
1) We assume that space is well, just space. (clarification: in relation to things that might create gravity)
2) We assume gravity comes from mass, instead of toward mass.
There are many research papers on the effects of gravity on gamma rays, but I haven't seen one the other direction.
If you model gravity as an unknown force that exists in all of space, like a bunch of particles we aren't aware of, then think of gravity as a "push". Every positive mass gets met with negative "push". This might match the space-curve such that, when two planets are next to each other, of same mass/volume/density, then space's all-around "pushing" from all of outside is equal, except between them, since the planets themselves would be blocking their sides. There's less "push" between them, so the outer ends push them toward each other.
If you use this view, and your question, then you can think of gravity as an unseen... particles/force/thing that exists inside atmospheres, outside atmospheres, and possibly between molecules and atoms themselves.
We then run into the time dilation, or relative motion, of which I don't have a solid answer, but in this respect, we begin to view time dilation as a possible relative effect on our "pushing through space" speed vs our "From-mass gravity velocity". I would say it runs into the realm of possible undiscovered "friction" between mass and gravity. Free-falling indicates no resistance to gravity, but standing on Earth will give a constant resistance of 9.8ms^2. If we view it as pressure from space-created gravity and not mass-created gravity, our ability to predict relative times takes a new angle, one that might be more accurate, or not, after enough testing.
I am summarizing years of reading as a hobbyist and theories. I am trying to present a possible viewpoint to model and test mathematically, and not some random speculation. Gravity itself models a system that matches the density of a pressure system with different density than other things (mass accelerating matches a balloon ascending), however since gravity is a unified field, I can't assume it's just pressure