Not familiar with the book, but I can't fault the fictional character's comment to any great degree.
Fiction is fiction, anyway.
While I do prefer an author be at least a little familiar with things like firearms and martial arts used in the story line, I also realize that many of them may have never held a firearm nor practiced any form of self defense. I've picked up quite a number of books written by authors I've never read and browsed through them at random, considering a purchase, only to find some really silly comment involving firearms or knives. That's enough to prevent me from buying a book.
If the closest an author ever comes to firearms is reading a gun magazine (or reading gun forums on the internet), maybe the author might want to avoid using those subjects or trying to write about them to any great extent. Many authors manage to write about such things in a general manner, placing the emphasis on the characters and not the weapons.
Then again, when discussing firearms and training I'm known for often saying something to the effect, "It's just a handgun".
I prefer to direct the focus of the person with whom I'm working more toward their knowledge, skillset & mindset. A reasonable familiarity & understanding of the safe handling, manipulation and use of the gun being used is needed, obviously, but obsessing on caliber performance and other perceived ballistic attributes shouldn't distract from its usage (accurate shot placement).
Yes, throughout my career at different times I've carried off-duty weapons ranging in caliber from .22LR to .44 Magnum, so I realize that caliber and inherent "power" can vary ... but they're still just handguns once you include shotguns and rifles using defensive ammunition. (The newest handgun hunting calibers & models, such as the .500 S&W Magnum and .460 S&W Magnum, are reaching up into the rifle power range, but they were intended to be used as hunting arm, after all.)
FWIW, I tend to look at consistently demonstrating proper trigger control, even under stress, as being a bit akin to knowing how to properly & effectively form a fist for striking. It's either done right or it's potentially problematic at an inopportune time ...
When I train & practice with my various handguns I'm focusing on my skillset, not any perceived attributes of the caliber. Also, mindset is mindset, and not dependent upon caliber.