It is not totally linked to your question, but there is a interesting point of view .
(Ref : T. Padmanabhan, Gravitation -Fundations and Frontiers, Cambridge, p.259)
If you consider a observer with $4$- velocity $u^i$, then, from Einstein equations, you have :
$$R_{ik}u^iu^k \sim T_{ik}u^iu^k$$
The first term $R_{ik}u^iu^k$ is the scalar curvature of the spatial sections as
measured by the observer.
The second term $T_{ik}u^iu^k$, is the energy density as measured by the observer.
So, instead of looking at $T_{ik}$ and $R_{ik}$ alone, we could see them as part of invariants, these invariants being different if they imply different observers with different $4$-velocity.