That was probably both true, and slightly misleading. I remember a talk on Drizzle (a MySQL fork looking to clean up and streamline the system after Oracle's buy) years ago where they touted similar numbers in code reduction by dropping support for all non POSIX or edge case OS's other than Linux, FreeBSD, and OS X (and that last one might have been added later). That is, they ripped out the HP-UX, AIX, Solaris and Windows specific code (and possibly more). Sybase looked to support a similarly diverse group of operating systems[1], so there were probably a lot of gains to be had even if they didn't remove all POSIX support.

1: http://infocenter.sybase.com/help/index.jsp?topic=/com.sybas...