The late Donald Crabtree was the dean of american knapping with obsidian. his french counterpart who worked flint couldn't even work with obsidian without considerable practice. The stuff will literally flake to one molecule thick ( I know, I saw one under an electron microscope.)
Crabtree in fact made up a surgical kit for his heart surgeon. the doctor had to practise using the tools, retraining his hand muscles to the greater cutting ability. Crabtree underwent heart surgery, and the finer incisions healed so rapidly glass instruments are now common.
That is sharp. But the advantages of metal gives us different standards. I don't make many fuzz sticks in the wild places out of paper. Testing the knife on what you actually do, like our member butchering game is the best guide.
In the real world, there is sharp,and there is sharp.
An apocryphal story is worth remembering. During the Crusades, King Richard met Saladin ( in reality, they never met.)
Richard drew his great sword and with a thunderous shout cut an anvil in half.Saladin threw a silk sash into the air, turned his scimitar blade upwards and watched the falling silk fall in two pieces.
Meanwhile, I believe several ancestors of contemporary knifemakers were stabbing castle walls.