Allyson discusses the unique application of Warmboard S in the French eclectic apartment renovation. By using Warmboard S instead of Warmboard, they were able to achieve a more even transition between different floor levels in the apartment without compromising the overall experience of the space. This decision was part of a value engineering exercise to stay within budget while maintaining the quality of the renovation. Allyson emphasizes the importance of considering budget constraints without sacrificing the integrity of the project.