A key point is that they have not measured the effect yet so it's not known whether the entanglement will be measured. Both papers describe a gravitational enta

A key point is that they have not measured the effect yet so it's not known whether the entanglement will be measured. Both papers describe a gravitational entanglement detection through measurement of evolution of a separate quantum phenomenon (e.g. nitrogen spin in a diamond lattice). One challenge, which is commonly a problem for laboratory gravitational experiments, is that many other force interactions dominate over short distance scales (electric, magnetic, or even vibrational phonons) so excluding those is critical to showing the entanglement is gravitational. This means near perfect electrical, magnetic, and vibrational isolation... and probably measuring their coupling amplitude them to show that it is perfect. As usual in experimental physics, the problem is not in detecting the effect, but in not detecting all the other interfering effects. It borders on proving a negative.