📝H. G. Muller wrote on Fri, Apr 24, 2015 08:32 PM UTC:
I don't know where you got that from. According to my information, Chu Shogi was already mentioned in manuscripts dated as early as 1350AD. A diary entry from 1424AD mentions a Shogi match played in front of the emperor, where one of the players was handicapped by a Free King. So that was certainly not referring to Sho Shogi. It was apparently considered so evident that 'Shogi' would mean Chu Shogi that the qualification 'Chu' was omitted. Tsume problems dating from 1675AD, 1697AD and 1746AD are all Chu Shogi problems; no historic problems or game records from Sho Shogi are known from that period or earlier.
All this is described in the Middle Shogi Manual, which was compiled in cooperation with the research group on the history of Shogi at the University of Kyoto. What are your sources?