This keeps getting weirder.
Plaza Swash is a postscript type 1 font. When I point the fontconverter web app to it and click convert the fontconverter simply states "Invalid font file, did you remember to choose one?" But this font shows up in Word, etc. so I know it's ok.
In the Mac world you typically use Fontbook to manage fonts for the system and that's seems to be how Gimp reads all the other fonts. Plaza Swash is only the second additional font I've installed, the first being Edwardian which works perfectly in Gimp. But I still can't get Plaza Swash to show up and it's very frustrating. No matter where I put this font Gimp doesn't recognize it. Why would that be?
I would not trust Word for whether a font is good or not. I would trust Scribus because I know it will not load questionable fonts. Have you thought about loading the font in FontForge, Inkscape Font Editor or a similar font program and exporting from there?