“In the absence of full mobilization by the Russians, the troop balances will swing in favor of the Ukrainians”
The reason the Russians are in Kherson is that there was no Ukrainian army in the region. They were in the east and defending Kiev and in the first week the Russians walked through the south.
The army that is closing in on Kherson is one that didn’t exist two weeks ago. It is reservists, experienced foreign fighters, and veterans.
There are about 1 million completely green recruits being trained across Ukraine. It will take time to turn these folk into a credible force, but in a couple of months Ukraine will have massive numerical superiority.
Russia's advantage was biggest early in the campaign. But the monger it drags on, and if the West is willing to keeps supplying the Ukrainians, the advantage inevitably will swing over to the Ukrainians simply because their usable manpower reserves are so much greater.
Russia obviously has more total manpower, but there no hint that the Russia of 2022 is anymore willing to have a mass mobilization and accept mass casualties than was the Soviet Union in Afghanistan, or Russia against Chechnya.