It is not, because to completely failed out of training there have to documented examples of why that individual can't perform the job. We make every accommodation to see if they can perform. However, the job requires you being able to work at any hour, thus they aren't able to perform the duties of the job.
It sounds like you're arguing for the title here. You say the job requires you to work at any hour, among other things. You say the lessons are at 6 in the morning. You say 80% fail. Sure, it doesn't conclusively prove that people drop out because of those two things, but it seems likely.
"However, the job requires you being able to work at any hour, thus they aren't able to perform the duties of the job."
That is why it is survivorship bias. You are assuming that it is possible for everyone because you and your coworkers were able to do it, while ignoring the fact that many people flunked out because they couldn't do it. That is what survivorship bias is.
Survivorship bias is when the people who survive don't understand why other people failed. We understand why they failed and the most common reason is that most people aren't comfortable making quick decisions where people's lives are at stack. Time of day usually isn't a factor here, but people's confidence in themselves to trust their training and decisions. The other reason is people just can't handle the shear amount of knowledge (rules) required to perform the job. Such as not everyone can become a surgeon due to the education, skill-set and intelligence required not every person can due air traffic control.
As you said earlier, some people drop out because they can't work at all hours. You don't know why, but you are assuming that it is because they don't work as hard as you . Hence survivorship bias. People who drop out for reasons other than not being able to work effectively at all hours are irrelevant.
The only way you can 'drop-out' per-se is if you diagnose yourself with 'fear of controlling'. Meaning the job scares you, outside of that you cannot just quit.
