Welcome Aboard!
No, you've done nothing wrong. You might be interested to know that by-and-large most Subsim members are quite familiar with the story. One of the missions in the old Silent Hunter II was to attack Scapa Flow. It was even the subject of the final episode of The Silent Service, a TV show back in the '50s that was otherwise exclusively dedicated to US submarine operations.
That said, this version is well told and well worth reading. Thanks for sharing it.