Why some warship design studies are better documented

Why is more known about the J3 battlecruiser than other designs considered at the same time?

J3 generated more reports and recorded design work, and more of those documents survived.

Some preliminary warship designs are easier to reconstruct because the navy produced more reports and conducted more recorded work on them. Later historians can only use the documents that survive. The uneven record therefore reflects both the original design process and archival survival, rather than an equal body of evidence for every option considered.