For example, what equations will describe the physics in a black hole?
No one knows yet.
For example, how can one optimally design a minimum-phase digital filter?
The answer is: not all the criteria for optimum design are clearly stated
in the white paper literature or in the technical books.
1. Some of the math has not been discovered yet (per Peter Thiel).
2. Some of the math has been discovered, in the company-private realm.
This condition might be common in many disciplines.
Whatever the case, Peter Thiel is right.
Many more math discoveries are yet to come. One way or another.