Youkoso Jitsuryoku Shijou Shugi no Kyoushitsu e: 2-nensei-hen Volume 9.5 Discussion

Did i understand it right that these .5 chapters are basically like filler volumes (but canon) the author might as well wrote a volume later ?
There were a couple things that mattered but nothing that can't be summarized in 2 sentences and quickly mentioned in the next book.
Like, i don't remember the last .5 volume but last (Y1) Christmas was definitely a .5 book as well.

Just a thought, doesn't matter much. Just that i thought this volume was kind of a slog.
Also, is it just me or is it getting kinda depressing lately ? After uninhabited island 2 he was basically all alone on the ship. Just like Christmas in 9.5 here.
Either he gets into class wars trouble or yet another girl confesses to him. But at the end of the day and 8 outta 10 days he frigging alone.
His relationship with Kei is doomed as well. He clearly doesn't feel shit towards her (at all or anymore, did he ever really like her in the first place, don't think so). But the 3 weeks definitely put an unrepairable rift into their 'relationship'.

Furthermore, this more and more feels like he will just quietly disappear, maybe even before the 3rd year ends.
I hope this continues even after school and he frees himself from the white room. I wouldn't mind another 4 years in University and beyond.