First, just as a point of fact, WhatsApp is mostly mobile development and network engineering messaging systems, not web development. Disciplines that one would normally classify under "software engineering".

Second, you appear to be confusing Fundamentals of Engineering exams and Principles of Engineering exams. There is no Fundamentals of Engineering exam for any engineering discipline, including structural, electrical, etc. Only the PE exam focuses on individual disciplines. FE is for...fundamentals.

Finally, and ironically, they do in fact make a Principles of Engineering certification exam for software engineers[1]. It's been offered for almost 5 years now. As of last year, the majority of states offered the exam and license software engineers just as they do other engineering candidates.

1. http://ncees.org/about-ncees/news/ncees-introduces-pe-exam-f...