There is no redundancy. Learning and teaching (yourself) are not synonymous. Learning is a result of successful teaching (yourself) or studying. For example, I teach my students but learning happens inside their heads. I hope they will learn but it is not a given. Similarly, it is possible to study/teach yourself but still to learn very little. The sense to me is that they need the desired outcome 'learn' so must go through the process 'teach themselves'.

I don't think it's redundant because teach and learn are different processes. Learning is often a passive activity, especially at the lower levels of learning, like habituation. I doubt you're familiar with these unless you've had formal training in learning theory. Learning is much, much, much more than what students do in school; its how animals adapt to their environments. Teaching is always an active process and thus "teaching themselves" isn't made redundant by the use of "learn" in the sentence.

Everyone thinks differently in this world.