Very possible washer bottle was in the way of some modification added. May have been removed and since it has a sensor leaves a message. Or sensor is dead and since it's 20+ years old a new one is hard to come by and he actually has washer fluid in there. Or any other of the annoying reasons that keep most people from owning 20 year old vehicles
Looks like a 99 FRC, not a Z06. Based on the lack of rear brake ducts and Z06 instrument cluster. Correct me if I wrong as I am curious if you know the year of the car? Beautiful work on the car and filming.