One idea about dark matter is that the laws of gravity are just different at large scale. This measurement rules out some of those theories ...

> the [measurement] enables us to test a certain class of modified gravity theories, which dispense with the dark matter paradigm and reproduce Modified Newtonian Dynamics (MOND) like behavior in the non-relativistic limit. Such modified theories of gravity have been dubbed “Dark Matter Emulators”. Some examples of these Dark Matter (DM) emulator theories include Bekenstein’s TeVeS theory and Moffat’s Scalar-Tensor-Vector gravity theory

Some attempts at explaining the missing matter involved modifying gravity to the effect that light and gravity waves would arrive at different times. They didn't so those theories are invalid.

"emulator" seems to be a term for a certain sort of model and simulation.