Not exactly. It's because he has his hands full As I mentioned he is either working on the Maseki Web Novel, Mastermind Web Novel or Mastermind Light Novel but never all three simultaneously. He had been focusing updating the Maseki Gurume Web Novel from November 2023 to April 2024.
Also, he seems to be taking the Light Novel of Mastermind pretty seriously as he seems to be put a whole lot of effort in improving the story, adding more plotlines and development or totally revamping the story as a whole.
You can respect him or feel annoyed with him for continuing to work on the Maseki Gurume Web Novel despite the fact that Mastermind is clearly the more popular series of his and with bigger demand for it in both the Web Novel, Light Novel and Manga even many of his readers are annoyed by his priorities.
This was his recent message from last April regarding the Mastermind Web Novel which I google translated. I could link you his Kakuyomu page for the source which includes all his status notes if you want.
"Thank you for always visiting us.
This is Yuki. Today, we have announced the release date for the 4th volume of the original work! "
"The latest Volume 4 is scheduled to be released in June. This volume will be the same volume as the 3rd volume, which is the thickest volume already published, and we have continued to add tens of thousands of characters!"
"In addition, Nakamura-sensei has already provided us with some wonderful illustrations so we hope to be able to show them to you all someday! Reservations have not yet started, but we have worked hard to prepare the 4th volume, so please look forward to it."
"Speaking of release dates, Reincarnated as the Mastermind of the Story 4 comic is approaching. The comic version is scheduled to be released on April 26th, so please enjoy it first! Don't miss the heated battle scenes drawn by Segawa-sensei and the magic sword from the climax of the 1st volume of the original work!"
"Next, I apologize for taking so long to update the web version... We have been working on the book version and other projects at the same time, so we are making you wait longer than expected. However, although it has taken some time, we are not planning to stop updating the web version. Therefore, we would appreciate your continued support."
"Just like the book version, we will prepare this version so that everyone can enjoy it , so please continue to support us...! We will occasionally announce the progress of the book version and the web version on x (twitter)!"
"If you would like, we would appreciate it if you could check it out! We have only given you the release date and an update on our current situation, so we will stop now for today. We hope you will continue to support "Reborn as the Mastermind of the Story"