Im not sure who he talked to but i speak to GREDDY japan daily, and yes you are correct all technicians other than two (emanage and suspension) speak only japanese. In sales YUKO, RYO, LIU and Daniel speak fluent english but they will not take general calls or enquiries from the public.
That said GREDDY brakes are designed to run off factory master cylinders, i have asked this question in the past when building the supra and onselling GTR parts in the past. i have the 6 pot fronts and 4 pot rear on the supra with std mastery and it is awesome.