There's only so much JSF can do to promote new seniors under the GP assignment rules. Kazuki aged out of juniors with only SB 51 scores, a wonky 3A and an inconsistent (and often under-rotated) 4S, and yet juniorish skating. He was not guaranteed any GP spots until Dice (who was initially assigned the host spot) pulled out of NHK Trophy due to pneumonia, and got lucky again with Yuzuru's withdraw from Worlds and Mura's retirement. Kudos for Kazuki doing so well in both events where he was a late substitute, and now that he is guaranteed 2 GP spots next season I hope he can make the most of his opportunities.
You are right, Kazuki got the spot on NHK because of the sudden illness of Dice, not because of Yuzuru's injury. I mixed up those two incidents, but now I remember.
And I agree with your assessment on Kazuki as well. Despite of the success at the recent Worlds, maintaining two spots for the following season is not going to be easy for him, but I really hope he will fight for that well.