In my opinion that's something the website owner should handle and it's a tracta...

stjohnswarts on April 9, 2021 | parent | context | favorite | on: W3C slaps down Google's proposal to treat multiple...

In my opinion that's something the website owner should handle and it's a tractable problem. It shouldn't be pushed to the browser other than as you mentioned through capabilities like SOP and cookies. The way it is is fine.