That's a good point, systems vary. That recommendation was for a 3 lecture hour per week course (there are additional tutorials, etc), and a full course load would be 4-5 courses a term. So that arithmetic gets you to 50-60hours/week in total, which is about right. With an easier course load the expectation might be 40hr/week.

The expectation is you would spend some time in formal lectures, some in tutorial sessions (usually with graduate student assistants) and some on your own - in roughly equal proportions.

I did teach some courses with more time in formal lecture (per week) and less in tutorial sessions, in which case the ratio would be adjusted to end up at around the same place.