Actually, you got it just backward.
The Ukraine tried and tested tactic is to back off, allow a small salient to form and then kill all the attackers. The Russians having no commanders close to the battlefield get sucked in and then killed every time. The successful tactic has been used over and over and over for months now.
Bahkmut is now a salient and the Russians are thinking they will close the envelopment. Unfortunately, theu lack the combat wherewithal to do the job
