Koga used the"Greg Herbold geometry" Miyata frames until 1995. From the 1996 model year Koga still used the Miyata name but went a totally different path with materiaIs and geometry. I live near the Koga assembly factory and know the range quite well. I understand Koga had to make a move after years of using the typical Herbold geometry but the change wasn't for the better.
The frame in your link is post 1995. These were sold a lot here in The Netherlands and are offered weekly here secondhand. Could be a nice basis for a build though.