A forum member who goes by the name Myrddin was quick to point out that the Sepia adjustment has a bug. It does two things … one, it seems to produce a result equivalent to the Black & White adjustment. And two, if you undo it, it doesn’t produce the right result. It breaks the history system, essentially.
So, just to warn everyone. The 3.20 Alpha is way cool (not that I’m biased), but stay away from Sepia for now. I’ve found the bug, and the fix will be in the next update. Thanks for your patience.