OK, I just tested it:

In terminal 1, I created a database and added a table to it:

  $ sqlite3 testdb
  sqlite> create table test (col int);

  $ gdb sqlite3 `pidof sqlite3`
  (gdb) b unlink
  (gdb) c

  sqlite> insert into test values(123);

  $ cp testdb-journal testdb-journal.save

  (gdb) c

Back in terminal 3, I sent SIGKILL to sqlite3, simulating a power failure:

  $ killall -9 sqlite3

  $ mv testdb-journal.save testdb-journal

This proves int_19h and I are right - if the journal file comes back, SQLite will apply it and roll back a committed transaction.

I then confirmed with strace that, as the documentation says, the directory is only fsynced after unlink when synchronous=EXTRA. It doesn't happen with synchronous=FULL. So you need synchronous=EXTRA to get durability in DELETE mode.