If that is the case, then chkn you should try the last commit of April (9c21813960fb) which is one commit prior to when the font styles stuff was integrated for the first time. You should probably try the commit after that too.
However, by the look of your second screenshot, I’m not so sure that is the problem. The OSXTypeface looks right, it has a proper font name and font style, so the conversion from default font names to actual font names worked fine.
What version of OS X are you using?
Have you tried the plugin in other mac hosts? Do you see the same issue?