In addition to contrived examples impairing comprehension I even think a real-world example fails to help the reader capture the most important piece of information about design patterns, and that's the context around when to use them. Giving a worked-out example while teaching the concept has the limitation that the reader didn't discover the pattern themselves in code, instead it was ripped out of a code base and handed to them without context of its use. And instead of seeing it as an option that was selected to be used in a particular code scenario it is instead presented as a fully-worked solution that can be plugged in anywhere and describing when to use it in words isn't as effective as discovering it being used in a code base you've been learning from.

Quite frankly, in my radical opinion, I think learning about programming through reading about it (books, articles, blog posts, etc) isn't very useful once you are past being a beginning programmer. To be a better programmer reading code is the only way I've seen good progress with learning new abilities that don't cause me to over-engineer my own solutions. This might not work for everyone but for me reading code daily has been a silver bullet to programming knowledge that a book or design pattern article could never capture for me.