They do not say for certain that the Hubble team's estimate is wrong. But they have injected new uncertainty into the question of how well the leading goal of the Hubble telescope program has been achieved. Basically, astronomers are trying to pin down what they call the Hubble constant - a number that reflects the expansion rate of the universe. The farther away a galaxy is, the faster it moves away from us. The Hubble constant specifies how fast a galaxy recedes given its distance.
Astronomers can measure the recession speed fairly accurately.
Getting accurate distances is trickier. Astronomers use what they call Cepheid variable stars to measure distance within a few tens of light years of Earth. These stars brighten and dim with a rhythm that reflects their natural brightness. The Key Project team used more than 800 Cepheids in 18 galaxies as much as 65 million light years away as part of its effort to determine the Hubble constant to within 10 percent. Maoz and his colleagues brought these figures into question by showing that the Hubble team's calculations based on Cepheids may be wrong.