It's meant to be shareable. So people can show this (and other tricks) to their tech-illiterate relatives and bond over things iPhone can do. It's all document

It's meant to be shareable. So people can show this (and other tricks) to their tech-illiterate relatives and bond over things iPhone can do. It's all documented in the user manuals (inside Books app) and the support pages. So I wouldn't necessarily call them "hidden" features.