I actually prefer it the way it is now. For me, private mode is effectively an extra temporary profile that is full featured, but wiped once the last window is closed. I usually don't need more than one.
But I understand that other people have other needs. It can be very useful for developers for instance. Make it an option, maybe.
I see both. I wouldn't want every tab to be separate but I occasionally want to have more than one independent private profile at a time. It would be nice if I could do this. Any sort of ephemeral container tabs option would probably satisfy this option and could maybe even remove most of my use of private browsing if I could just open ephemeral containers in an otherwise regular window.
Unfortunately it doesn't work like a separate profile for extensions so you can either enable them and trust that the extension doesn't leak data from private windows into your main profile or you can disable the extension - there is no option to enable the extension but enforce that the extension sticks to the private profile (with possible exceptions for extension settings which should persist).
But I understand that other people have other needs. It can be very useful for developers for instance. Make it an option, maybe.