Yet this seems to be exactly what the pro-war Z patriots were demanding Putin do. Why do the Z patriots have such a profound inability to relate to their own history.

You might see this as if pro-Z people are asking the state to continue the war and the state complies but it's the other way around. The state intentionally supports and cultivates them by spreading dehumanizing propaganda, fake news, alternate history, anti-scientific bullshit and by limiting access to other sources of information (either by banning them or by using firehose of falsehood).

Ukrainian officials have been stating (multiple times now) they will not negotiate with Russia if it keeps bombing civilian infrastructure

No wonders Ukraine doesn't want to negotiate. There's not even a hint of a goodwill on Russian side.

Ukraine has an upper hand on the battlefield and estimates that it might win the war in near future. And here's Russia that offers to freeze the war at extremely unfavorable conditions with a very big chance that there could be another invasion attempt withing a few years.

They also see that winning this war likely could give a finishing blow to Putin's regime while negotiations would solidify his position.