It seems weird to comment on issues in the afterward (specifically the one for volume 2), but it seems like the translation for part of it has to be wrong, because the author is thanking the publisher for being allowed to advertise his "new" work despite it being under a different publisher, and that "new" works is Magic Stone Gourmet.
I must also give thanks for being graciously allowed to advertise my new work in this afterward despite it being under a different publisher. It'll be published under BOOKS and is called Magic Stone Gourmet.
The first volume of Sundering Fate was published in Japan in August of 2022 (and the second volume was published in March of 2023). The most recent volume of Magic Stone Gourmet was published in Japan in June of 2021. So, the entirety of what he's released for Magic Stone Gourmet came out before even a single volume of Sundering Fate came out. So, calling Magic Stone Gourmet a new series in the afterward for any volume of Sundering Fate doesn't make any sense.
So, I don't know what the afterward for volume 2 actually says in Japanese, but I don't see how it could say what the English version currently says about Magic Stone Gourmet being a new series.