Just like Stargirl and some other recent shows, The Winchesters prepares for the likelihood of cancellation and prioritizes giving us a well rounded story rather than a cheap cliffhanger that may, like so many others from the past decades, never get resolved.
I'm not a big fan of this show or even this episode; storywise I would have preferred a prequel over an alternate timeline but I'll admit it was good seeing the old faces, especially Dean's and it's good to know that they haven't completely given up on continuity. As has been noted the main plot was rushed but I didn't care about it anyway and for the aforementioned reasons I give it an 8/10 (while the show is a weak 7) and I will probably include this episode in any future rewatch since it does make for a better send-off for Dean.
TL;DR They tried something with this show, it didn't quite work but after that became clear they were gracious enough not to try to overstay their welcome.
I'm not a big fan of this show or even this episode; storywise I would have preferred a prequel over an alternate timeline but I'll admit it was good seeing the old faces, especially Dean's and it's good to know that they haven't completely given up on continuity. As has been noted the main plot was rushed but I didn't care about it anyway and for the aforementioned reasons I give it an 8/10 (while the show is a weak 7) and I will probably include this episode in any future rewatch since it does make for a better send-off for Dean.
TL;DR They tried something with this show, it didn't quite work but after that became clear they were gracious enough not to try to overstay their welcome.