I'm not sure I understand those docs about pin 4. So is it an input or an output for the IIgs? You're thinking that it should be left floating, rather than connected to GND on the Floppy Emu board? Or should it be driven high (to 5V)?
As a test, you could try physically cutting off pin 4 from Floppy Emu's DB-19, or use a cable and cut the pin 4 wire. It shouldn't affect the behavior when used on a Mac, since there are three other ground lines already.
As a test, you could try physically cutting off pin 4 from Floppy Emu's DB-19, or use a cable and cut the pin 4 wire. It shouldn't affect the behavior when used on a Mac, since there are three other ground lines already.