I have read Are casters aware of spell slots?, but this question is aimed at the mechanics in general, not just spell slots
In our own world, there are millions of people working around the world trying to understand every detail of the world. We have distilled the most basic of physical laws into mathematical formulae, separated every element known to man in the tiniest of particles, measure every aspect of the world and have created experiments that are so delicate that the morning dew on the grass outside the testing facility can throw off results. We've even created a global infrastructure meant to share that information for the betterment of all.
Now, I might be overestimating the inquisitiveness of the inhabitants of Toril, but I would be surprised if the Arcane Scholars of Candlekeep or the Red Wizards of Thay or any other of the many academic groups in the Forgotten Realms aren't investing a large amount of time into working out the mechanics of their world. Stuff like the damage a spell does or the amount of damage a kobold or gibberling can take or the increased potency of an Adamantite improved longsword or any other game mechanic. They might even be going into the deeper statistics of the world, like wanting to quantify how much better one fighter is compared to another, and end up figuring out the Strength/Dexterity/Constitution/Intelligence/Wisdom/Charisma abilities. And maybe, just maybe, they have stumbled upon clues that everything in Toril depends on random chance that a character can have limited impact on.
In our world, a lot of these details don't really matter as much: it might improve our society in the long run by allowing us to create better technology, but we're not really going to get better food by improving the accuracy of the Avogadro constant. However, in a magical world where a lot of things revolve around combat, knowing that Magic Missiles do up to 4 damage each and how many of these you'll probably need to finish off that ogre can really mean the difference between life and death. And knowing just how strong each of your soldiers are and how much stronger each of them will get from that enchanted sword your court merchant bought from an adventurer can end up drastically changing the course of a war.
So I'm wondering: How aware of game mechanics are the NPCs of Toril, and especially the smarter ones who do the magical research or are in positions of power? Are they actively using this knowledge in their quest to improve the world? Is it even possible that someone created a compendium of the entire world that explains this in detail, and is selling this book to enterprising adventurers? And yes, I am alluding to the possibility of the Player's Handbook being an in-game resource people can buy and read.