Unfortunately this is a follow up to the fact that the JBC are unsure how Ishida's stamina and body will cope at Heavyweight. They were wanting him to take part in either a 6 round bout or another public exhibition before allowing him to fight Fujimoto for the Japanese Heavyweight title.
With Fujimoto and Ishida fighting anyway in a non-title bout, it seems the JBC have put their foot down rather than risk serious injury to Ishida, pictured.
We would expect that if Ishida is "competitive" against Fujimoto and survives the 6 rounds unscathed, the JBC would allow a rematch over 10 rounds for the Japanese title. It's a shame that they've not allowed the bout to be a 10 round bout though we can understand them being cautious and not wanting to see a fighter hurt.
This bout, on April 30th, is set to be part of "Kamikaze 3" which also features a Japanese Lightweight title contest between Yoshitaka Kato, the defending champion, and the big hitting Yuhei Suzuki as well as a bout involving the once touted Kenji Kubo,