I posted this on the Finale forum, but I thought I would mention it here: MakeMusic did mention in passing that the new SMuFL fonts in Finale have been revised and improved over their original counterparts.
So, here is the sfz glyph in Maestro:
... and here's the sfz glyph in the new Finale Maestro:
All credit for this work goes to Mark Adler, who made the font over six years ago, after which time it presumably sat waiting for Finale to add the SMuFL plumbing.