In the zwift world, there is an alp du zwift climb that is a great test of ~1 hour power. When I was training for a race w long climbs last year, I did it in 50 minutes @ 97% of tested ftp. It was a really hard effort, but I could have dug out another 3% and another 10 minutes if it were a real race situation. I agree that you need to have trained for long hard intervals to hit a tested ftp for an hour, but i expect most people just don’t have a good enough reason to try. It’s a miserable exercise.