A little context about metadata management:
When we introduced calibre-managed collections for Sony readers some four years ago there was a firestorm of protest about how calibre was destroying a user's carefully prepared work. After a lot (weeks) of discussion and negotiation we came up with the three options you see today. They are intended to have the following semantics:
- Manual. When a book is sent to the device, calibre will add that book to collections specified by calibre's metadata. Calibre will never remove a book from a collection. This behavior preserves a user's hand-built collections, with the cost that a book can remain in collections that are no longer appropriate.
- On send: When a book is sent to the device, that book is removed from any collection of which it is currently a member, then added to collections as indicated by calibre's metadata. This behavior prevents calibre from changing collections for other books, including ones that calibre does not know about. It also does not update collections when calibre's metadata changes.
- Automatic. Calibre is to manage all collections on the device. Every time the device is connected or a book is sent, collections are rebuilt to correspond to calibre's current metadata values. No user-added collections survive this process.
Given these semantics, on-send management equals automatic management only if every book on the device is resent on every connection.