I am fairly certain that the limit on the IIgs was actually the quality and availability of the CPU. WDC had serious yield issues, and this even affected accelerator availability for the Apple IIgs which were less plentiful than the machine itself (obviously). Hence, Woz said 8MHz at the start but this didn’t materialize. Part of this is due to the CPU design not working on smaller nodes that WDC had hoped would lead to the increased clocks. Ultimately, it was second sources and redesigns that helped the chip make its way into the SNES and other machines.