The issue with Putin is I don’t even think he knows exactly what his end game is in this situation. (I was going to reply to a previous post but this thread moves so quickly it’s tough to keep up).
Diplomacy works if there is an actual clear outcome. Putin has moved the goalposts constantly. He keeps on asking for different things so how do you negotiate with someone like that. Does he want to “de-nazify” Ukraine (which is laughable)? Does he want to demilitarize Ukraine? Does he want the Donbas to become independent or to take it into Russia? Does he want Ukraine to say they will never join NATO or the EU? These are conversations which will have to be had now but pre war it wasn’t clear exactly what his aim were. So how do you deal with that diplomatically?
The first paragraph is more or less how negotiation works. You're not supposed to fixate on an ideal point. You're supposed to have a range.
It helps, if you're trying to land in that range in bargaining, if everyone else has some idea where that range is. (This is what your second paragraph is getting at.) That doesn't generally lead to a better bargain, but it makes obtaining a bargain more likely. Concealing preferences tends to lead to advantage if a bargain obtains, but also tends to make the bargain less likely to obtain.
What I think has happened here is that Putin has learned, through experience, that concealing his preferences tends to lead to better outcomes. He now has little idea about what to do when he is in a situation where he is probably better off cutting a deal sooner rather than later. As is so common in sequential international crises, he has learned that escalation tends to lead to better outcomes than forthright bargaining. He therefore is reading from the wrong playbook when dealing with opposition that no longer will back down from further escalation.