This is interesting and makes some sense to me or am I reading it wrong?
I do wonder if this is the trap everyone was worried about, Russia was never going to be able to realistically hold the far bank in any numbers as they would be subjected to accurate artillery and HIMARS strikes, so pulling back a large part of their forces to cities to preserve them makes sense.
Ukraines problem now is with Russia withdrawn across the Dnipro and having destroyed most of the crossing points, if Ukraine crosses in force to liberate cities and cut off the main supply route, they will themselves be subjected to the same issues Russia had, ie an in ability to supply the front line due to limitations of getting supplies, munitions and replacement across the river.