It is an interesting format, but a bit hard to discover. If it would not have been for your comment, it would not have occurred to me, that there is a second level which enriches the overall topic.
Is it essential to the format to open all secondary parts at once? Otherwise that would be a great use case for the details/summary tag, which also would come with affordances that indicate that there is more information available.
Thanks for that feedback - I will think about how to make the parts beyond the tip of the iceberg more obvious and discoverable. Philosophically, I want the "tip" to be as uncluttered as possible but ... we'll see what I can come up with.
Theoretically, if enough people began writing in this form it would then become obvious by virtue of familiarity ...
It is explained here:
https://john.kozubik.com/pub/IcebergArticle/tip.html
“An Iceberg Article is a single page of writing which links to a larger collection of supporting documents, resources and services.”