That question made me DuckDuck into the matter and necromance a bit.
Maybe F(x) is referring to someone not so prominent but still involved in E7/N950/N97 design, but those names pop up most frequently.

Axel Meyer was the lead designer for n97 and also at least involved in n9.
Eguchi Shunjiro was involved in n97 and also E7.

N9 "family" was concepted by Anton Fahlgren.

Then there was mighty Marko Ahtisaari as Head of design during the time.