it's not NCESS that requires it to be a supervisor but rather certain states that require it. My guess is that NCESS will accept it. Whether that counts towards applying to get a license or take a test in a certain state is a whole other question.
As
@NY-Computer-Engineer stated above It will vary from state to state. Some states require that it be a supervisor, some will say that it can be done under the guidance or review of a PE who is not a supervisor. Some boards are more forgiving in their definition of "supervisor" than others. You should check your own states regs to be sure.
I
know NCEES will accept it, but the state may be different.
I'm dealing with this right now. I took and passed the Power PE exam in April 2018 (1st attempt - one and done baby) but now I'm going through all the licence application fuss. Here in Oregon, you take the PE exam first. You do not apply for licence until AFTER you pass the PE exam. So after I passed it, I created an NCEES record. Oregon says they accept NCEES Record rather then filling out all of the entire Oregon forms. I went that route because I also intend to apply for license in WA (I live in Portland, OR, but my office is across the river in Vancouver, WA and my job involves work in both states), so I figured NCEES record would save me time and save my references from having to fill out all the reference paperwork two or three times.. (apparently NOT, but more on that later...)
I listed 5 PE's that I work along side of, as personal references, and my supervisor separately in the work history section. (my supervisor is NOT a licensed PE). NCEES contacted all 5 of my PE personal references, as well as my actual supervisor, and after a few weeks NCEES approved my NCEES Record and marked it verified, complete, and ready for state board submission. I then filled out the required other sections of my Oregon licence app and sent it in, as well as transmitting my NCEES record (the NCEES record cost $100, just FYI).
I
THOUGHT that from there I was in the home stretch and the Oregon process would be minimal, since NCEES already contacted, verified and approved my references and work experience. WELL, to my surprise
, and my 5 references and supervisor's surprise, my references told me that Oregon state has now been emailing them asking for them to verify my work experience
all over again (WTF was the point of the NCEES Record then?!?!
And will WA do the same?) I hate bugging people 3 times to do the same thing and the whole reason I did the NCEES Record was to avoid that hassle and burdening 6 people 3 times each.
So anyway, that answers that yes, NCEES can accept it, but who knows what your state will do.
Sidenote: I'm a federal government employee and since there are so few PE's in the FED, there is an exclusion that alloys fed employees to become a PE even if their work experience wasn't under direct supervision of a licensed PE.