I was going to say that, based on this guy's album list, I wondered if the reading of Hiroshige came from Nirareba's list of composers, which had some errors in it.
But they had the name as Hironari over there too, so I dunno. ¯\(º_o)/¯
Revoc hasn't really been active recently, so maybe shoot him a PM to see if he remembers where that reading came from?