Emphasis mine
§ 37.32. References for certification as an engineer-in-training or licensure as a professional engineer.
(a) A candidate for licensure as a professional engineer, and a candidate for certification as an engineer-in-training who seeks to qualify for the examination based on experience, shall provide as references the names and addresses of at least five persons who can attest to the candidate’s good moral character and who either directly supervised the candidate or can otherwise verify the candidate’s experience. At least three of the references shall be professional engineers licensed in the United States who are unrelated to the candidate. The remaining references may be professional land surveyors, professional geologists or unli-censed engineers who, through education and experience, possess an equivalent level of expertise as that of a professional engineer. A reference who is not a professional engineer licensed in the United States is required to submit a curriculum vitae.
I know this doesn't really answer your question. Ideally there would be a PE in your line supervision who could attest with a straight face that they were your "manager" and checked your technical work over the years. If that's not the case then your supervisor will need to submit their CV.