To clarify my earlier point: the author isn't trying to build a practical calculator or generate human-readable algebra. Using exp and ln isn't a cheat code because the goal is purely topological. The paper just proves that this massive, diverse family of continuous math can be mapped perfectly onto a uniform binary tree, without secretly burying a state machine inside the operator.
They use the complex version of logarithm, that has a lot of branching problems.
So it isn't exploiting the branching for computation.
For example, IIRC ln( -inf.0 + y * i ) = ´+inf.0 + pi * sign(y)