If that's the case then I'm not sure why the Ukrainians are even negotiating. Unless Russia is offering to withdraw from Ukraine's internationally-recognised borders with minor preconditions, the Ukrainians should walk away from the table.
Because the Russian army is still there and if needed, Russia could just declare full mobilization and zerg rush Ukraine.
The problem is that Russia DOESN'T want to declare full mobilization because then they'd have to explain why their "special operation" in Ukraine suddenly needs them to start throwing soldiers at it like it's WW2. So they are using everyone and anyone they can simply "write-off" without having to commit all their forces.
This war is going badly for Russia but make no mistake, Ukraine is still in pretty deep shit. I am very impressed with how they have held out thus far.