There is than one way to get the same apparent expansion in space-time.

Say we started with mass M confined to a given volume V. If I was to explode that mass so the volume doubles; mass density halves, space-time will expand around the mass due to GR. On the other hand, if we started with M confined to volume V, and expanded space-time, so the apparent volume doubles, it would look like the mass is expanding. Both scenarios look the same, but cause and effect is opposite in each case.

We can expand a mass; bomb, to make local space-time expand in the lab. But has anyone done the opposite and expand space-time in the lab, first, to show it is possible for this to lead the mass? We do this on paper with dark energy, but dark energy has not been seen in the lab to prove it is real and not just a placeholder.

Say we had a uniform cloud of water vapor, that occupies volume V. Next, we cool the cloud and allow the water vapor in the cloud to condense into millions of little water droplets. This will alter the space-time profile of the cloud. Space-time will contract, at each water droplet, compared to the original uniform cloud due to increases mass density. While space-time will expand the space, between each droplet compared to the original cloud, due to lowered mass density in the dead space.