In answer to the original questions - yes they can plan more than 13 and no there are no laws say they can’t.
In the same way, dependant on your contract of employment there is nothing to stop the boss only planning you a 6 hour day and 18 hours off.
Having been involved in running a fleet, we planned for what we needed doing for the good of the company and within EU Drivers Hours rules. If a driver couldn’t or wouldn’t do what we planned, we changed the job and didn’t force anyone. If it was occasional and seemed genuine then no problem. If - as happened - it was the same guy every time and he seemed to think he made the rules then it would be treated differently.
If a driver constantly pulled the “I’m tired card” we would question his health and suitability for the role. This would mean a “welfare interview” to discuss his health and work life balance. The end result might mean we feel we could only give the driver 8 hour days or maybe 10 hour days as we ‘care about his health’. Ultimately I would win, within the law, and the driver would move on and be a pain somewhere else because his earnings were down. I would be able to fully justify my actions and show in any court I was a caring sharing employer.
Employment is a two way street. Give and take. Swings and roundabouts.
The answer to this thread has been given many times. There’s no actual laws, just common sense. If you don’t like the job - go find one that suits you.