Safari has done this for a long time when you have multiple tabs with similar titles open.
I think the intent is to increase the unique text within the tab titles when you are reading sites that have titles like "My Blog - Tuesday's Article" and "My Blog - Wednesday's Article"; otherwise these would both shorten to "My Blog - ..." as tab count increases, or as other tab width constraints come in to play.
Granted, the heuristic for identifying common text between tabs isn't always great and can sometimes just result in titles looking cut-off.
I think the intent is to increase the unique text within the tab titles when you are reading sites that have titles like "My Blog - Tuesday's Article" and "My Blog - Wednesday's Article"; otherwise these would both shorten to "My Blog - ..." as tab count increases, or as other tab width constraints come in to play.
Granted, the heuristic for identifying common text between tabs isn't always great and can sometimes just result in titles looking cut-off.