Hello. Can you please explain me how could you follow a course on quantum mechanics without previous knowledge on quantum mechanics? That's the normal thing! You don't do calculus with a prerequisite of knowing calculus! Also, how can you do quantum computing without knowing about quantum mechanics? Seems non-sense to me. I only know that that quanticized things are values in terms of natural numbers, quantas. And you can no longer predict the behaviour of a certain particle (say an electron) because it follows a probabilistic behaviour. My mathematics and physics knowledge is still weak. 

The quantum computing course was one that didn't require previous knowledge in quantum mechanics.

To be more precise, the quantum mechanics course required previous knowledge in Calculus and Linear Algebra, and the quantum computing course required only Linear Algebra (you can check the link I added before). 

I also should make clear that I'm not talking about advanced level quantum mechanics or advanced level quantum computing here, but beginner/introductory level (first/second-year undergraduate physics level).

The quantum computing course covers the basics of quantum mechanics but using a different method than a quantum mechanics course would as I explained before (and also refreshes your linear algebra knowledge). You finish the quantum computing course with a basic understanding of quantum mechanics (which I argue would be a stronger foundation than you'd get from a normal quantum mechanics course), then you can continue on and do a quantum mechanics course (which I argue would now be easier to follow). And if your goal is to just learn quantum mechanics, then you have quantum computing knowledge as a bonus as well as knowledge of some other subjects as I explained above. 

Hope that explains my point of view.