Exactly. Russia's claim that this shift is due to their good will in the peace talks is simply a political fig leaf to cover a military failure and subsequent military decision to pull back. Russia will want to shorten the lines to achieve a more sustainable position, but I doubt they will withdraw from the Kyiv region entirely because by maintaining a presence there they tie down Ukrainian forces that would otherwise be available to reinforce the east.
I think at this point there is no reason to pin down Kyiv's forces, if they do reinforce the east what is there to stop Russian from bombing those reinforcement in the open?