http://bugs.winehq.org/show_bug.cgi?id=30557
--- Comment #6 from Rafał Mużyło galtgendo@o2.pl 2012-05-21 11:26:15 CDT --- Actually, it's more like they were of opinion, that it's not working correctly in some of the cases and as that it couldn't be fixed, so they simply removed the option to break things, when they've made glib initialize threads unconditionally.
TBH, this implementation, wine tries to use, seems a bizarre mix of pthreads and Windows threading - IIRC it was already (that is: before glib 2.32) not working correctly some of the times.