It's an incredible tool. Especially since Carroll has ADHD as well and kind of "invented" the Bullet Journal over time to manage himself.
I tend to add "Inboxes" to the general method. I might not have the journal with me at every minute, or it might be inconvenient to use it in certain situations (i.e. I prefer paper journal, but in meetings a digital format has it's advantages). So I have an "Inbox" (basically a daily log) on my Phone & Work PC. At the end of the day, I go through the additional Inboxes as well and condense everything into my central (paper) journal.
For me, it's better to have a small number of additional but convenient places to write down stuff than skipping the journaling just because I don't want to pull out my journal during a meeting.
Jessica is such a great person and educator.
She is actually more commonly known for her YouTube channel. (Search "How to ADHD"). She has A LOT of content there and her book is basically the paper version of her videos and insights.