The "was a real person" was also something that I had debated on for a while with my supervisor in regards to potential validity issues. I originally wanted to go for something along the lines of 'personally knew you' or 'was here with me,' however, upon conducting some literature review on studies regarding vTubers, it was found that vTuber audiences intentionally separate the vTuber avatar from the real person voicing them. Because of that, we ended up using "was a real person" as the final phrasing of the question.
Here's the paper in question that delved more into it if you wish to read further:
https://doi.org/10.1145/3411764.3445660
Though it's important to note that the interview conducted in that paper was done with a China-based demographic, which may be different to the western approach of the perceptions towards vTubers.