What Li Zheng didn't know was that Guidance did have the ability to predict. The All Things Analysis ability could allow him to understand the laws of the universe's operation, and simulate future events in a way similar to "foreknowledge," accurately predicting the future state of any matter.
Although this ability also has limitations, such as with Emperor Zhao and the Black Tide God, these supreme Rule Controllers' variables are difficult to control.
However, a Destiny Rule clearly falls within the realm of analyzable simulation.
It's just that the energy consumed for this kind of simulation is terrifying, way beyond what players like Li Zheng can afford to play with. One must completely decipher all operational trajectories on a micro level of the Destiny Rule, and the resources invested are even scarier than making a rule.
This is also the reason Guidance answered that it was not feasible.
