Space-time, by the very definition of what it is, contains space.
You're a physicist? Where did you get your degree from? What company do you work for?
I do not answer irrelevant questions prying into my identity , thanks for understanding .
''In physics, spacetime is any mathematical model which fuses the three dimensions of space and the one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive differently where and when events occur.'' Quoted from Wikipedia .
Space-time is a mathematical model , by space it means distance , not the actual space . That is the mistake you are making in your own understanding . You are considering space and quantum fields are as one , that is not the case !
Space-time is an exceptionally brilliant model that allows us to predict things , comet vectors for example .
The Universe is visually expanding , we observe this because of the red-shift of distant visual bodies . Quantum fields can expand with increased energy as can matter , metal for example . Expansion , curvature is all relative to flat space that is independent of all matter .