DS got started on his diss in the summer
Wow. That was early. Surely he wouldn't have covered all the course content by then? DD had a full term of lectures and seminars during the autumn term, and the students on DD's course had to submit the topics they were interested in at the end of November. They didn't get to find out their question until after Christmas.
They still hadn't done all the modules by the time they had to choose so DD chose the topic that she had acheived the highest marks in. They then did cancer biology, and she enjoyed it so much she was sad that she hadn't chosen that as her main topic, but she didn't know whether she would like it or not.