I don't know why such an accomplished bowyer has extra stipulations with FF type materials, but that's nowhere near the strangest thing I've heard concerning strings.
A FF string won't change the draw force curve--the feel of the draw won't change. I'd be very surprised to see a gain of 8 fps too, with equally well made strings. There's just not normally much of a performance gain by shaving a few grains of weight off the string.
The main advantages to a FF type string is increased durability and reduced stretch/creep, at least with a moderate strand count. With a little tinkering and tuning, you should be able to get any string very quiet, at least if the bow design will allow it.