When I began music classes in school at a very young age, a few of our classmates had perfect pitch. One class focused on sight-reading melodies. The teacher went around the room and called on each of us to sing a specific section.
I definitely did not have perfect pitch and I used every creative excuse to get out of these exercises. I could hear the melody in my head but simply couldn't reproduce it in sound. I knew absolutely and instinctively when someone else got a note wrong but I could never sing it myself. Our perfect pitch friends looked at the melody and sang it perfectly.
Thankfully, the teacher realized I would never be able to do that and eventually stopped calling on me (the rest of the class also appreciated that!). I could play the melody on violin and piano, but could never sing it.