As far as we know, was this only shown posthumously? Perhaps its the equivalent of Rest His Soul. Maybe its more formalized so Greystone is put on the names of knights or those killed honorably, while something like Whitestone is given to an important clergy member after s/he (well this is Ishgard, most likely he) died.
It reminds me of a friend who, due to confusion over language and foreign birth certificates, briefly went by the surname "sex:male" for a period of time.