If this is impacting your productivity take a moment to create a radar or duplicate the one mentioned by @Pat, it is likely that it will get fixed sooner.

Could you clarify what when running on newer versions of macOS available in Xcode 13 Beta, available today. means? Do we have to update both Xcode and macOS? Is there any workaround to fix the issue on Xcode 12? The performance issue is major and unfortunately not everyone can jump to the latest version of Xcode right away.