Everyone starts out with the best intentions for their study periods (free periods). I will do my homework for that day, catch up on any work, start assignments, won't have as many subjects to worry about etc. Which are all fine reasons, the only problem is the vast majority of students will have these reasons but once they get the study periods the treat them like free periods and just waste time.
I had 3 study sessions a week (75mins each) in year 12, only because I completed accelerated IPT in year 11. When I had assignments/assessments to do I did try and get as much done as possible, or homework etc. But looking back a lot of those study sessions were wasted browsing the Internet, random walks and leaving school early.
And as for people getting what seems like more study periods/sessions it really depends on how your school structures your timetable and the length of your periods/sessions as to how many you will get.
So to answer the thread question. In theory yes they are but 9/10 in practice no they are not.