One thing I love about B-sides in general is that they can be very interesting experiments in their own right and it's fun to speculate on why they left it off the record. In the case of AFI, generally it seems like their desire to move forward led them to scrap stuff they felt was too played out - Fainting Spells sounds like it could be one of the earliest Sing the Sorrow songs, even with the electronic breakdown. Too Late For Gods could have been a Decemberunderground song, though it's not foggy enough. The View From Here though seems to defy that explanation as it's definitely one of the most unique songs in their catalog and epitomizes the experimental spirit they were trying to achieve with Decemberunderground, far more than any other song on that record.
That's one of the things I'd thought about Sing the Sorrow: It sounds different at first but when it actually comes to the way they were writing the songs, they're still using a lot of the same chord progressions and arrangement tricks from the last two albums; it's just tuned half step down, a little slower, and more ambient sounding. The B-sides from that record only seem to support that hypothesis give that away too much; it's like they thought writing "Synesthesia" and "Reivers Music" (and I guess, to a lesser extent, Now the World, ironically one of their more harmonically complex songs) wasn't going far enough away from the Art of Drowning sound. Death of Seasons and The Leaving Song are the only songs on that Sing the Sorrow at that classic AFI fast tempo, with parts of Girl's Not Grey and Bleed Black coming close.
By the way, if Rabbits are Roadkill did end up on Sing the Sorrow like Adam wanted, it might have gone between Girl's Not Grey and Death of Seasons. Or maybe Dancing Through Sunday and Girl's Not Grey. Definitely somewhere in the second quarter of the record.