It can be a reeeeaaaallly effective study method.
One of my friends wrote six practice exams last year for methods and spec because he had already burned through all of the practice exams he could get his hands on. Guess who got a 50 in methods and a 48 in spec last year?
tbh im gonna play the devils advocate here...
If he burnt through all the practice exams he could get his hands on he would've known the content extremely well allowing him to create practice exams... coz there's hella practice exams online you can find so many easily
dont think writing practice exams led to that result but rather him burning through all the exams
but yeah writing questions is good if they're solid questions. I've tried it previously but didnt find it very effective coz the things i needed to practice werent things i knew i had to practice if that makes any sense.
Writing questions for your friend and they write questions for you would be effective in tackling this though.