Not just the credits, but the interview on bizmash! revealed Murata's role was to provide art for the remake that the both of them were working on from the start. Same with NEETSHA's interview with ONE himself.
So the assumption that Murata is actually writing all the extra is just that, entirely your assumption, not substantiated by actual facts we know, which says otherwise.
I mean, sure, you're free to believe whatever you want, but I'm gonna need a bit more evidence to claim their statements false.Especially when you know, Murata has NEVER written serialization on his own in his career. Ever. Across all three serializations.
Only time we ever saw Murata as the writer are shorts, every serialization he's ever had in his career were written by someone else. (And even talking about his one shots, half of them had other writers lol.)Does he have creative inputs? Of course he does, you can't co-produce a manga without it from the artist.
Do we have any evidence of him doing the actual writing of extra story? Not to my knowledge, no.… are YOU? Can you provide me some source?
Sure I cannot.
Simply last chapter feels like something Murata would do on his own, not like cooperation with One. Tournament idea also feels like something that does not fit for current arc and looks "filerish" while there is enough of content from Ones OPM for Murata to draw for years to come.
Though on other hand One and Murata did together that "Cockroach" one shot that was rather bad in my opinion, so maybe its not beyond One to make something just "OK" or not special at all I guess..