I wonder about Hersh. I respect his sources but he too certainly can get misled by them.
But I admit I agree that I think the Ukrainian army has sustained enough losses that they would mutiny if pressed much harder. Attacking in WW I was always much more costly than defending. I'm confident the same dynamics apply today.
I hope the West is not pressuring Ukraine to attack but instead that they decide for themselves how best to go forward. Yet if they decide to accept the frozen situation but wish to resort to guerrilla warfare I have to think that would trigger unintended consequences.