As the universe expands, galaxies disappear beyond the observable universe. So we could calculate the rate of expansion of the universe (the Hubble parameter) by estimating the rate of disappearance.
Now imagine if an astronaut leaves his spaceship and orbits around a black hole for a long time, and returns to the spaceship. Perhaps billions of years have elapsed for those on the spaceship, but only hundreds of years for the astronaut. They can both agree on how many galaxies were visible from the spaceship at the start and finish of the journey.
However, they both must disagree as to the rate of disappearance of the galaxies. The astronaut calculated that the missing galaxies disappeared over a few hundred years, but the spaceship observer says it was over a few billion years. Therefore they would have observed two different Hubble parameters while the astronaut was travelling. Is this wrong?