Which applications are you referring to? I could criticize these apps with the same logic, honestly. Plus, it breaks the visual hierarchy, causes the tabs DO modify the content of the menu bar above the tab bar.
UE4 was consistent will all major web browser’s tabs layouts, where the top edge of the screen is a valid tab docking location.
I cross my fingers that you’ll change your mind on that (or at least have a config to revert to the old tab bar location).