The ATTACH docs state:

Transactions involving multiple attached databases are atomic, assuming that the main database is not ":memory:" and the journal_mode is not WAL. ...

Should that first sentence possibly say:

... main database is not ":memory:" or "" ...

:-?

(The db name "" works like ":memory:" but uses a temp file. Or at least that's my understanding.)

Hypothetically, since there's no(?) way to re-open the same "" a second time, crash recovery could not take place with such a db?