You are not quite understanding the problem, they aren't confusing which lens goes in which eye, but which sideis the correct one. You wear contact lenses you should know what they are talking about. I really don't know how to explain the problem but ... you are misunderstanding it.
I've worn glasses for about 2 years now, I hated contact lenses because it also took me like half an hour to get ready, so I gave up on them and stuck to my glasses. But last year my pair of glasses broke and I couldn't afford new ones so I was forced to give contact lenses a try, and I was amazed by how easily I got used to them, and now I wear both, some days I wear my glasses, other days I wear contact lenses.