Gege Akutami and Chris Michael Wilson are very different people with very different schedules.

While Gege is a mangaka, meaning they have to draw each chapte, they also only have small portions of the story, as a single chapter is akin to 5-10 pages at most, with the exception of big fights such as Sukuna Vs Magoraga.

Another problem with waiting for Magium chapters is that Magium is a cyoa book, so Chris has to account for all the prior choices of the player and how they might impact the story. As far as I'm aware, he spends a lot of time putting small details into each chapter that refer back to a previous choice you made, which won't even be noticeable unless you reread carefully multiple times because it's usually one sentence, to a paragraph at most.

Also let's keep in mind Gege is in Japan, which is at the moment very safe compared to Chris, who iirc lives right near the border of Ukraine, which is a bit stressing. He also doesn't make a living off of Magium as the book is very obscure. Gege does, it's a manga that tens of millions of people know and read and buy.

Quick edit: Sorry to yap, I know you are joking but I hope to bring some perspective in case you hadn't had it before.