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.
It's a test that university graduates in the traditional engineering disciplines (civil, mechanical, etc.) usually take in the USA. After 5 years of work experience, you take another test, then your state's licensing board gives you a stamp and the credential "Professional Engineer" (P.E.). You can then take on liability for project documents that you stamp, so you charge clients/employers more money.
It's mainly useful if you work for a consulting company.
