The first problem is that a quantum theory of gravity is not straightforward. It's not "just" a spacetime with superposition, it probably has an even richer structure, the way QED has a richer structure than an EM field with superposition. And from the little hints we have it might have "spin 2" representation, and thereshould be some quantum very complicated field that acts like the metric GR field at low energies. But not only there are many possibilities for that, they are also very complicated, basically untreatable, or have infinite degrees of freedom in their definition itself.
The second problem is that there is no current way of experimentally probing such behavior. You say put a massive object in superposition, but to have observable effects you need to have so massive an object that is tens of orders of magnitude above "impossible".
This experiment is nice but it probes "just" the gravitational field of the Earth (a ~10^25 kg object). It is very nice for accurate time measures, and maybe for measuring gravitational fields, it comes nowhere near to probe quantum gravity effects, just quantum effects coupled to classical gravity (classic in the sense of GR but not quantum)
The curious thing in my opinion is how this will effect quantum computing. If gravity causes decoherence, then it is likely difficult to maintain coherence in large qubit devices that aren't in microgravity.
For example, I get entanglement. I can get answers to questions like "Is FTL comm possible? No." or "What is a practical application for entanglement? Quantum radar - sorting your initial emission from jamming." etc.
This though? Just too abstract (for me).
Seems like there is a lot of theory discussions around the Internet but not seeing any experimental evidence one way or the other in the first few results.
“Take the case where a massive object is put into a superposition of two possible locations at the same time. General relativity says that any object with mass should bend the fabric of space-time. But what if that object is in a superposition? Is the geometry of space-time also in a superposition?”
I don’t have a PhD in anything let alone physics, but it seems to me that answering the above question could potentially lead to a reformulation of GR in a way that gracefully incorporates quantum mechanics, which is worth getting excited about.
But yes, you’re correct that the nuance is lost on me. Still, there seem to be plenty of people who find it interesting.