@maisonaustyn Based on some of the afterwords by the mangaka and author that are at the end of the manga volumes (as well as based on the author writing a Veldora's Slime Observation Journal novel-like segments at the end of each manga volume), it does seem as though the author is involved with the manga to a certain extent.
(He was also involved in some parts of the anime, such as the Shizue and Diablo/Noir side-story, which is actually something that was referenced in LN vol 12 by Diablo, but that we hadn't got to see ourselves before that episode in the anime.)