Prolog is a programming language, and this isn't a programming language. Prolog doesn't process natural language by itself. Prolog isn't a tableau-based theorem prover.

This project is a natural-language-processing, tableau-based-theorem-proving application implemented in the Prolog programming language.

I mean how does the pruning constraint tree search applied in prolog implementations differ from the tableaux method

After some research, the tableaux method seems to require full coverage, which would only converge with the search tree if all conditions have to be exhausted.