Exactly right. Fun aside, there's no reason to try to make your turns flat. On some trainers, the ailerons aren't very effective at low speeds, so using rudder to turn when landing is a useful habit to develop. But of course that's rudder in the direction of the turn. I find it hard to believe that you get "tighter" turns by using opposite aileron and rudder. For a really tight turn you can lay it on its side and give it a lot of up elevator. If using rudder in a turn causes you to bank too much because of roll coupling, the best technique is to add less rudder, not to use opposite aileron.

Some day, when the OP is beyond trainers, using opposite rudder in a turn is going to cause his plane to spin. A stall won't make you spin if you're coordinated when the stall occurs, even in a turn, but if you're not coordinated, it can get exciting.