Gee, didn’t a “consensus” of scientists agree that Einstein was correct...the science is settled. Anyone who disagrees is an Einstein “denier”. This is how “climate science” works so why not apply it here?
Partly because this article is saying that one of the two radical Theories that Einstein proposed to radically change the dominant view of how the universe worked, including multiple specific predictions that could be observed might have relatively small error in one very important value. The article doesn’t say it, but this not going to be accepted in the scientific community without significant proof. If there is real work proof that light is observed moving more slowly than Enstien predicted, such as that supernova, then scientists will attempt determine whether there are other factors that slowed that light from its predicted speed, such as traveling through matter (like one poster said) or some gravitational effects. The problem is that other measurements based on the constant of speed of light in a vacuum have held up, but the speed of light in the almost vacuum of space might not be one of them. This proposed photon disintegration theory of light propagation seems to be more complicated way of explaining and observation, but we’ll see. Either way, this guy makes some predictions that can be tested, they will be tested, and we’ll move the discussion forward.