I've heard that Keyshot isn't a physically correct render engine. It actually simulates physically correct renderer. Is it right?
This information can be found on the KeyShot.com home page:
"KeyShot is built on Luxion's internally developed, physically correct render engine based on research in the areas of scientifically accurate material representation and global illumination."
So, the answer is: yes, it is physically correct.
Of course, anything taking place in software inside a computer is a simulation. No matter what. Like living inside The Matrix. If you want real light you have to be out in the real world, in a real room lit with real lights or under the real sun.